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lwsshak3 answered: 6491 problems
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Trigonometry-basics/691934: `Find a value of theta in [0, 90](degrees) that satisfies the statement. Leave the answer in decimal degrees rounded to seven decimal places, if necessary.
cosine theta= 0.1879656.
I know the answer is 79.1659173, but I don't the steps to solve it. Can some help me please? Thank you
1 solutions

Answer 426934 by lwsshak3(6493) About Me  on 2012-12-10 01:37:14 (Show Source):
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Find a value of theta in [0, 90](degrees) that satisfies the statement. Leave the answer in decimal degrees rounded to seven decimal places, if necessary.
cosine theta= 0.1879656.
I know the answer is 79.1659173, but I don't the steps to solve it. Can some help me please? Thank you
**
This is how to get the answer with a calculator:
set your calculator to 7 decimal places.
Use the inverse cos key and enter 0.1879656.
You will then see displayed the answer:79.1659173º


Trigonometry-basics/691970: Evaluate the expression.
cot^2(90)-sec(180) both in degrees.
The answer is 1 but I don't know how to solve this. Please help.
1 solutions

Answer 426933 by lwsshak3(6493) About Me  on 2012-12-10 01:20:48 (Show Source):
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Evaluate the expression.
cot^2(90)-sec(180) both in degrees.
The answer is 1 but I don't know how to solve this. Please help
**
cot(90)=cos(90)/sin(90)=0/1=0
cot^2(90)=0
..
-sec(180)=-1/cos(180)=-1/-1=1
..
cot^2(90)-sec(180)=0+1=1


Linear_Equations_And_Systems_Word_Problems/691655: clara is one third her sister's age 4 years later clara will be 3less than half her her sister 's age what was clara s age 3 years ago
1 solutions

Answer 426796 by lwsshak3(6493) About Me  on 2012-12-09 02:50:39 (Show Source):
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clara is one third her sister's age 4 years later clara will be 3less than half her her sister 's age what was clara s age 3 years ago
**
let x=clara's age 3 yrs ago
x+3=clara's present age
3(x+3)=sister's present age
4 years later:
(x+7=clara's age
(3(x+3)+4)=sister's age
3less than half of sister's age=(3(x+3)+4)/2-3
x+7=(3x+9+4)/2)-3
x+10=(3x+13)/2)
2x+20=3x+13
x=7
clara's age 3 yrs ago=7


Exponential-and-logarithmic-functions/691473: Juan is going to deposit $1,000 in an account that will earn him compund interest. The account pays 8% interest, compounded monthly. How much money will he have after 10 years?
1 solutions

Answer 426795 by lwsshak3(6493) About Me  on 2012-12-09 02:12:32 (Show Source):
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Juan is going to deposit $1,000 in an account that will earn him compund interest. The account pays 8% interest, compounded monthly. How much money will he have after 10 years.
**
compound interest formula: A=P(1+r)^n, P=initial investment, r=interest rate per period, A=amt after n periods.
For given problem:
P=1000
r=.08/12
n=10*12=120
..
A=1000(1+.08/12)^120=2219.64
How much money will Juan have after 10 years. $2219.64


logarithm/691550: Solve the equation.
(x^3)(9^x) -9^x =0
1 solutions

Answer 426794 by lwsshak3(6493) About Me  on 2012-12-09 01:54:47 (Show Source):
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Solve the equation.
(x^3)(9^x) -9^x =0
9^x(x^3-1)=0
9^x≠0
x^3-1=0
x=1


Quadratic-relations-and-conic-sections/691313: find vertex, focus, and equation of directrix of y^2 = 36x
1 solutions

Answer 426791 by lwsshak3(6493) About Me  on 2012-12-09 01:45:25 (Show Source):
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find vertex, focus, and equation of directrix of y^2 = 36x
This is an equation of a parabola that opens rightwards.
Its standard form of equation: (y-k)=4p(x-h), (h,k)=(x,y) coordinates of the vertex.
For given equation: y^2=36x
vertex:(0,0)
axis of symmetry: y=0 or x-axis
4p=36
p=9
focus: (9,0) (p-distance to the right of the vertex on the axis of symmetry)
directrix: x=9 (p-distance to the left of the vertex on the axis of symmetry)


Quadratic-relations-and-conic-sections/691434: Find the standard form of the equation of the hyperbola with the given charateristics and center at the origin Foci:(+-10,0) Asymptotes:y=+-3x
1 solutions

Answer 426788 by lwsshak3(6493) About Me  on 2012-12-09 01:33:12 (Show Source):
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Find the standard form of the equation of the hyperbola with the given charateristics and center at the origin Foci:(+-10,0) Asymptotes:y=+-3x
**
This is a hyperbola with horizontal transverse axis.
Its standard form of equation: (x-h)^2/a^2-(y-k)^2/b^2=1
For given hyperbola:
center: (0,0)
slope of asymptotes=±3=b/a (for hyperbolas with horizontal transverse axis)
b=±3a
c=10 (distance from center to foci)
c^2=a^2+b^2=a^2+9a^2=10a^2
100=10a^2
a^2=10
a=√10
b^2=c^2-a^2=100-10=90
equation: x^2/10-y^2/90=1


Quadratic-relations-and-conic-sections/691496: graph the ellipse using the proper algebra
x^2+(y^2/12)=1
1 solutions

Answer 426787 by lwsshak3(6493) About Me  on 2012-12-09 01:01:03 (Show Source):
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graph the ellipse using the proper algebra
x^2+(y^2/12)=1
This is an equation of an ellipse with vertical major axis.
Its standard form: %28x-h%29%5E2%2Fb%5E2%2B%28y-k%29%5E2%2Ca%5E2=1, a>b, (h,k)=(x,y) coordinates of center.
For given equation: x^2+(y^2/12)=1
center: (0,0)
a^2=12
a=√12≈3.46
vertices: (0,0±a)=(0,0±√12)=(0,0±3.46)=(0,-3.46) and (0,3.46) (y-intercepts)
b^2=1
b=1
x-intercepts:(±1,0)=(-1,0) and (1,0)
see graph below as a visual check on the foregoing algebra:
y=±(12-12x^2)^.5



Trigonometry-basics/691292: Find the amplitude, period, and phase shift of the function, and graph one completed period:
y=1+COS (3X+pie/2)
1 solutions

Answer 426750 by lwsshak3(6493) About Me  on 2012-12-08 20:16:52 (Show Source):
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Find the amplitude, period, and phase shift of the function, and graph one completed period:
y=1+COS (3X+pie/2)
**
Equation for the cos function: y=A)cos(Bx-C), A=amplitude, period=2π/B, phase shift=C/B
For given equation: 1+cos(3x+π/2)
Amplitude=1
B=3
period: 2π/B=2π/3
1/4 period=2π/12=π/6
phase shift=C/B=(π/2)/3=π/6 (to the left)
..
Graphing:
I don't have the means to graph the function for you, but I can show you how to develop the coordinates with which you can draw the graph:
Start with the basic function: y=cos x with a period of 2π/3
coordinates: (0,1), (π/6,0), (π/3,-1), (π/2,0), (2π/3,1)
shift to left (π/6): (-π/6,1), (0,0), (π/6,-1), (π/3,0), (π/2,1)
bump up 1 unit: (-π/6,2), (0,1), (π/6,0), (π/3,1), (π/2,2) (final configuration


Trigonometry-basics/691480: Find sin x/2, cos x/2, and tan x/2
from the given information.
sec x = 10/9 ,270° < x < 360°
sin x/2=
cos x/2=
tan x/2 =

1 solutions

Answer 426739 by lwsshak3(6493) About Me  on 2012-12-08 19:23:13 (Show Source):
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Find sin x/2, cos x/2, and tan x/2
from the given information.
sec x = 10/9 ,270° < x < 360°
sin x/2=
cos x/2=
tan x/2=
**
sec x=10/9=hypotenuse/adjacent side
hypotenuse=10
adjacent side=9
opposite side=√(10^2-9^2)=√(100-81)=√19
sin x=-√19/10 (in quadrant IV where sin<0)
cos x=9/10
..
Identities:
sin x/2=±√[(1-cos x)/2]
choose positive root because x/2 is in quadrant II where sin>0
sin x/2=√[(1-cos x)/2]=√[(1-9/10/2]=√.1/2=√.05
..
cos x/2=±√[(1+cos x)/2]
choose negative root because x/2 is in quadrant II where cos<0
cos x/2=-√[(1+cos x)/2]=-√[(1+9/10/2]=-√1.9/2=-√.95
..
tan x/2=sin x/(1+cos x)=-(√19/10)/(1+9/10)=-(√19/10)/1.9
..
How to check answers with calculator:
sec x=10/9
cos x=9/10
cos^-1=(9/10)≈25.84º (reference angle in specified quadrant IV)
standard position of angle=360-25.84=334.16
x/2=334.16/2=167.08
reference angle=180-167.08=12.92º
..
sin x/2=sin 12.92≈0.2236..(in quadrant II where sin>0)
√.05=0.2236..
..
you can check cos x/2 and tan x/2 in the same way


logarithm/690518: Can someone assist me to express log[2](A)+log[2](B)-3log[2](C)as a single logarithm. Thank you very much!
1 solutions

Answer 426635 by lwsshak3(6493) About Me  on 2012-12-08 02:50:40 (Show Source):
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Can someone assist me to express log[2](A)+log[2](B)-3log[2](C)as a single logarithm.
log2[AB/C^3]


logarithm/691065: Suppose that ln5 =S and ln11 =T. Use the properties of logarithm in terms of S and T
1 solutions

Answer 426634 by lwsshak3(6493) About Me  on 2012-12-08 02:46:45 (Show Source):
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Suppose that ln5 =S and ln11 =T. Use the properties of logarithm in terms of S and T
log5+log11=log[5*11]=S+T
log(55)=S+T


logarithm/691251: Find the domain of the function. (The 8 is supposed to be a subscript, for base 8)
f(x)= log8 (x+3)
1 solutions

Answer 426633 by lwsshak3(6493) About Me  on 2012-12-08 02:37:02 (Show Source):
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Find the domain of the function.
f(x)= log8 (x+3)
domain: (-3,∞)


logarithm/691298: g(x) = In (x-6) find the domain of the function.
1 solutions

Answer 426632 by lwsshak3(6493) About Me  on 2012-12-08 02:35:14 (Show Source):
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g(x) = In (x-6) find the domain of the function.
domain: (6,∞)


logarithm/691255: Use the Laws of Logarithms to combine the expression. (They are all base ten, because they have no base listed, but you probably know that already)
5log x - (1/3)log (x^2+1) + 4log (x-1)
1 solutions

Answer 426631 by lwsshak3(6493) About Me  on 2012-12-08 02:32:12 (Show Source):
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5log x - (1/3)log (x^2+1) + 4log (x-1)
log[(5(x-1)^4)/(x^2+1)^1/3]


Trigonometry-basics/690972: 1.) Solve each equation.
a.) log7(2x)^2+log7 (3)=2
b.) log4 (8)+log4 (x^2-8)=8
c.) log12 (-3a-8)+log12 (a+4)
d.) ln-3k=ln(-2k-4)

1 solutions

Answer 426576 by lwsshak3(6493) About Me  on 2012-12-07 16:56:09 (Show Source):
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1.) Solve each equation.
a.) log7(2x)^2+log7 (3)=2
log7[(2x)^2*3]=2
convert to exponential form
7^2=4x^2*3=12x^2
12x^2=49
x^2=49/12
x=±√(49/12)≈±2.02
..
b.) log4 (8)+log4 (x^2-8)=8
log4[8*(x^2-8)]=8
4^8=8*(x^2-8)=8x^2-64
8x^2-64=65536
8x^2=65536+64=65600
x^2=8200
x≈±90.55
..
c.) log12 (-3a-8)+log12 (a+4)
log12[(-3a-8)(a+4)]=log12[(-3a^2-20a-32)]=log12[-(3x+8)(x+4)]
..
d.) ln-3k)=ln(-2k-4)=?
ln argument mssing


Trigonometry-basics/691184: The following problems give an expression for one of the three functions sin , cos, or tan ,with (theta) in the fi rst quadrant. Find expressions for the other two functions. Your answers will be algebraic expressions of x.
(a) sin (theta) = 3/x
(b) x = 4 cos (theta)
(c) tan (theta) = x
1 solutions

Answer 426554 by lwsshak3(6493) About Me  on 2012-12-07 15:47:06 (Show Source):
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The following problems give an expression for one of the three functions sin , cos, or tan ,with (theta) in the fi rst quadrant. Find expressions for the other two functions. Your answers will be algebraic expressions of x.
(a) sin (theta) = 3/x
(b) x = 4 cos (theta)
(c) tan (theta) = x
**
Use the following notation: O=opposite side, A=adjacent side, H=hypotenuse
..
(a) sin (theta) = 3/x=O/H
O=3
H=x
A=√(H^2-O^2)=√(x^2-3^2)=√(x^2-9)
cos (theta)=A/H=√(x^2-9)/x
tan (theta)=O/A=3/√(x^2-9)
..
b) x = 4 cos (theta)
cos (theta)=x/4=A/H
A=x
H=4
O=√(H^2-A^2)=√(4^2-x^2)=√(16-x^2)
sin(theta)=O/H=√(16-x^2)/4
tan (theta)=O/A=√(16-x^2)/x
(c) tan (theta) = x=O/A
O=x
A=1
H=√(O^2+A^2)=√(x^2+1^2)=√(x^2+1)
cos (theta)=A/H=1/√(x^2+1)
sin(theta)=O/H=x/√(x^2+1)


Exponential-and-logarithmic-functions/690402: solve: log base a of x + log base a of (x-2)= log base a of (x+4)
1 solutions

Answer 426420 by lwsshak3(6493) About Me  on 2012-12-06 20:41:32 (Show Source):
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solve: log base a of x + log base a of (x-2)= log base a of (x+4)
loga[x(x-2)]=loga(x+4)
x(x-2)=(x+4)
x^2-2x=x+4
x^2-3x-4=0
(x-4)(x+1)=0
x=4
or
x=-1 (reject, (x-2)>0)


Exponential-and-logarithmic-functions/690548: Solve log 2x + log 12 = 3. Round to the nearest hundredth if necessary.
1 solutions

Answer 426419 by lwsshak3(6493) About Me  on 2012-12-06 20:33:47 (Show Source):
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Solve log 2x + log 12 = 3. Round to the nearest hundredth if necessary.
log 2x + log 12 = 3
log(2x*12)=log(10^3)
2x*12=10^3=1000
2x=1000/12
x=1000/24
x≈41.67


Exponential-and-logarithmic-functions/690550: Write the expression as a single natural logarithm.
2 ln x – 5 ln c
1 solutions

Answer 426418 by lwsshak3(6493) About Me  on 2012-12-06 20:27:51 (Show Source):
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Write the expression as a single natural logarithm.
2 ln x – 5 ln c
ln[x^2/c^5]


Exponential-and-logarithmic-functions/690554: Solve the exponential equation.
1/16= 64^(4x–3)
1 solutions

Answer 426417 by lwsshak3(6493) About Me  on 2012-12-06 20:24:58 (Show Source):
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Solve the exponential equation.
1/16= 64^(4x–3)
1/4^2=4^3^(4x-3)
4^-2)=4^(12x-9)
12x-9=-2
12x=7
x=7/12


Exponential-and-logarithmic-functions/690557: Solve the logarithmic equation. Round to the nearest ten-thousandth if necessary.
3 log 2x = 4

1 solutions

Answer 426415 by lwsshak3(6493) About Me  on 2012-12-06 20:19:19 (Show Source):
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Solve the logarithmic equation. Round to the nearest ten-thousandth if necessary.
3 log(2x) = 4
log(2x)=4/3
convert to exponential form
10^(4/3)=2x
2x≈21.5443
x≈21.5443/2
x≈10.7722


Exponential-and-logarithmic-functions/690558: Solve ln(5x + 7) = 8. Round to the nearest thousandth.
1 solutions

Answer 426412 by lwsshak3(6493) About Me  on 2012-12-06 20:12:15 (Show Source):
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Solve ln(5x + 7) = 8. Round to the nearest thousandth.
ln(5x + 7) = 8
convert to exponential form: base(e) raised to log of the number(8)=number(5x+7)
e^8=5x+7
5x=e^8-7
x=(e^8-7)/5
x≈594.792


Exponential-and-logarithmic-functions/690560: Use natural logarithms to solve the equation. Round to the nearest thousandth.
5e^(2x + 11)=30

1 solutions

Answer 426408 by lwsshak3(6493) About Me  on 2012-12-06 20:02:31 (Show Source):
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Use natural logarithms to solve the equation. Round to the nearest thousandth.
5e^(2x + 11)=30
divide by 5
e^(2x + 11)=6
(2x+11)lne=ln6
lne=1
2x+11=ln6
2x=ln6-11
x=(ln6-11)/2
x≈-4.604


Exponential-and-logarithmic-functions/690685: solve each equation for x by first rewriting both sides as powers of the same base. 32^x=64
1 solutions

Answer 426402 by lwsshak3(6493) About Me  on 2012-12-06 19:53:12 (Show Source):
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solve each equation for x by first rewriting both sides as powers of the same base.
32^x=64
(2^5)^x=2^6
2^5x=2^6
5x=6
x=6/5


Exponential-and-logarithmic-functions/690845: Whats (5x)^(-1/2)=10? Steps please
1 solutions

Answer 426401 by lwsshak3(6493) About Me  on 2012-12-06 19:50:13 (Show Source):
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Whats (5x)^(-1/2)=10
(5x)^(-1/2)=10
1/(5x)^(1/2)=10
√(5x)=1/10
square both sides
5x=1/100
x=1/500


logarithm/690406: Log(base 9)(x-6)+log (base 9)(x-6)=1
1 solutions

Answer 426298 by lwsshak3(6493) About Me  on 2012-12-06 03:24:54 (Show Source):
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Log(base 9)(x-6)+log (base 9)(x-6)=1
log9[(x-6)(x-6)]=log9(9)
x^2-12x+36=9
x^2-12x+25=0
solve for x by completing the square
x^2-12x+25=0
(x^2-12x+36)=-25+36
(x-6)^2=11
x-6=±√11
x=6±√11
x=6±3.317
x≈2.683(reject, (x-6)>0)
or
x≈9.317



Trigonometry-basics/689854: To whom it may concern,
what is the relationship between cotangent theta and cotangent NEGATIVE theta? Can you please give me 7 or 10 examples to work with. I really need to learn this immediately for an upcoming exam. Please reply ASAP. A thousand thank yous won't be enough.
-Lex


1 solutions

Answer 426293 by lwsshak3(6493) About Me  on 2012-12-06 02:32:28 (Show Source):
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what is the relationship between cotangent theta and cotangent NEGATIVE theta?
cot(x)=-cot(-x) (this is called an odd function, compared to an even function)
Examples:
pick angle of 45º in quadrant I
this gives you a reference angle of 45º where cot 45º=1
-45º will also give you a reference angle of 45º but in quadrant IV where cot -45=-1
..
pick angle 135º in quadrant II
this gives you a reference angle of 45º where cot135º=-1
-135º will also give you a reference angle of 45º but in quadrant III where cot-135º=1
..
pick angle 225º in quadrant III
this gives you a reference angle of 45º where cot225º=1
-225º will also give you a reference angle of 45º but in quadrant II where cot-225º=-1
..
note: I used a reference angle of 45º for the examples but this will hold true for any reference angle.
This will also hold true for the tan function since cot is the reciprocal of tan.
A negative angle means rotating in a clockwise direction and a positive angle in a counter-clockwise direction.The value for the trig functions and their reciprocals is computed from the reference angle and the sign depends on which of the 4 quadrants the angle is in. See if you can apply this method to the sin and cos functions.
..
Hope this helps!


Trigonometry-basics/690368: Please help me solve this equation
use a double angle formulas to find the exact value of cos2u when sinu=3/5, where pi/21 solutions

Answer 426287 by lwsshak3(6493) About Me  on 2012-12-06 01:37:30 (Show Source):
You can put this solution on YOUR website!
use a double angle formulas to find the exact value of cos2u when sinu=3/5, where pi/2 ..
cos2u=1-2sin^u
=1-2*(3/5)^2
=1-18/25
=7/25
..
calculator check:
u=sin^-1(3/5)≈2.498 (in quadrant II)
2u≈4.9961 (in quadrant IV where cos>0)
cos2u=cos(4.9961)≈0.2799..
7/25=0.28


Trigonometry-basics/690393: simplify: -10 sin (2x+1) cos (2x+1)
1 solutions

Answer 426284 by lwsshak3(6493) About Me  on 2012-12-06 01:03:36 (Show Source):
You can put this solution on YOUR website!
simplify: -10 sin (2x+1) cos (2x+1)
use Identity:sin2x=2sinxcosx
-10 sin (2x+1) cos (2x+1)
=-5*2 sin (2x+1) cos (2x+1)
=-5sin[2(2x+1)]
=-5sin(4x+2)


Trigonometry-basics/690395: find all solutions of tanx + 1= 0, where 0 < (or equal to) X < (or equal to) pi
1 solutions

Answer 426283 by lwsshak3(6493) About Me  on 2012-12-06 00:57:56 (Show Source):
You can put this solution on YOUR website!
find all solutions of tanx + 1= 0, where 0 < (or equal to) X < (or equal to) pi
0 ≤ x ≤ π
tanx+1=0
tanx=-1
x=3π/4 (In quadrant II where tan<0)