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Tan(-5pie/12)
The formula is tan(s-t)=tan s + tan t/ 1+tans tant
or
tan(s+t)= tan s-tan t/ 1+tans tant 1 solutions
Answer 202101 by nabla(475) on 2010-03-05 19:14:40 (Show Source):
You can put this solution on YOUR website!Try:
To make this more natural, remember that the primitive tangent function has period of pi. So we have Tan(-5pi/12) congruent to Tan(7pi/12) mod pi.
Now: What functions do we easily know the value to for trigonometrics? pi/3 is certainly one. So, pi/3=4pi/12---> We need to know 3pi/12=pi/4 ! This is also an easy find.
So, we take Tan(7pi/12)=Tan(3pi/12 + 4pi/12) Now we use your formulae:
Tan(3pi/12 + 4pi/12)=[Tan(pi/4)-Tan(pi/3)]/(1+Tan(pi/4)Tan(pi/3))
Now it remains to remember what Tan(pi/4) and Tan(pi/3) are. We use the definition of Tangent.
Tan(x)=Sin(x)/Cos(x).
So Tan(pi/4)=1.
Tan(pi/3)=(sqrt(3)/2)/(1/2)=sqrt(3)
Finally, substitute into our expression:
(1-sqrt(3))/(1+sqrt(3))
Now, simplify:
 =  =
This could be done quicker, but I hope you can see the full details of what is going on through this procedure.
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Sequences-and-series/277627: ... 23, 25, 27, 29... which expression describes the sequence?
A. 3x - 3
B. 3 + 2x
C. 2x - 2
D. x squared + 1 1 solutions
Answer 202099 by nabla(475) on 2010-03-05 18:55:04 (Show Source):
You can put this solution on YOUR website!Try solving the equations for each term of the sequence.
Eg.
a. 3x-3=23? -> 3x=26 -> x=26/3 Hence x is not a natural number
b. 3+2x=23? -> 2x=20 -> x=10 Hence this is a possible solution
c. 2x-2=23? -> 2x=25 -> x=25/2 Hence x is not a natural number
d. x^2+1=23 -> x^2=22 -> x is irrational and hence not a natural number.
This gives (b) as the only possible solution as we define sequences such that terms are generated by natural numbers. You can easily check the remaining, given terms of the sequence.
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Geometry_Word_Problems/277639: x+7x=8x 1 solutions
Answer 202098 by nabla(475) on 2010-03-05 18:40:41 (Show Source):
You can put this solution on YOUR website!Perhaps it is best to think of "x" as something tangible in real life. Consider x as an orange.
On the left-hand side of the equation you have 1 + 7 oranges. On the right hand side you have 8 oranges. Does 8 = 8? Yes, always. So we will say the solution is x such that x is contained in all real numbers.
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Polynomials-and-rational-expressions/175746: This question is from textbook Algebra 2
How do I graph this polynomial function? f(x)=x^4 - 2x^3 - 3x^2 + 5x + 2.
Thank you very much. 1 solutions
Answer 130891 by nabla(475) on 2009-01-09 10:34:18 (Show Source):
You can put this solution on YOUR website!1) Factor to f(x)=(-2 + x) (-1 - 3 x + x^3)
2) The first evident, real root will be x=2.
3) It should be noted that this will "eventually" resemble a parabola. Moreover, our interest will be around x=2.
4) Techniques of calculus will give us concavity, max, min, inflection.
f'(x)=4x^3-6x^2-6x+5=0 gives criticals of
x -> -1.05274
x -> 0.611731
x -> 1.94101
If you test outside the intervals you will note changes in direction of the slope this is indicative of extrema.
Thus: x=-1.05274 is local minimum
x=0.611731 is local maximum
x=1.94101 is local minimum
Concavity [not entirely necessary]:
f''(x)=12x^2-12x-6=0
gives
x -> -0.366025
x -> 1.36603
Testing intervals again you will find CU on (-inf, -0.366025), CD on (-0.366025, 1.36603), then CU on (1.36603, inf).
This is certainly enough information to produce the following graph:
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expressions/175192: SIMPLIFY
30) -SR(16) =
31) SR(-16) =
32) SR(1/81) =
33) SR(25-16) =
34) SR(16-25) =
1 solutions
Answer 130270 by nabla(475) on 2009-01-06 08:03:40 (Show Source):
You can put this solution on YOUR website!30. -4
31. 4i
32. 1/9
33. 3
34. 3i
All of the above can be done by taking what is in the parentheses and forming a square. For instance -sqrt(16)=-sqrt(4^2)=-4.
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Linear-systems/163240: Solve using Cramer's Rule Solve for x and y:
x + 2y = 5
x - y = 3
1 solutions
Answer 120315 by nabla(475) on 2008-10-21 07:37:07 (Show Source):
You can put this solution on YOUR website!I will show you how to apply it:
for:
ax+by=e
cx+dy=f
We will have Cramer's rule giving us:

and
So, just plug in the numbers for the problem we're interested in. Namely, a=1, b=2, c=1, d=-1, e=5, f=3.
The process is done automatically by this web site:
Check:
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Linear-equations/161716: Solve the system of equations using the substitution method.
If the answer is a unique solution, present it as an ordered pair: (x,y). If not, specify whether the answer is "no solution" or "infinitely many solution."
7x+y=1
3x+2y=-9 1 solutions
Answer 119182 by nabla(475) on 2008-10-13 04:29:43 (Show Source):
You can put this solution on YOUR website!from the first:
y=1-7x
Put that y into the second equation:
3x+2(1-7x)=-9
3x+2-14x=-9
-11x=-11
x=1
If x=1,
y=1-7(1)=-6
check:
7-6=1
3-12=-9
yes.
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Linear-equations/160756: x+2y+z=1
2x+3y+2z=0
-x-3y+3z=1 1 solutions
Answer 118522 by nabla(475) on 2008-10-07 09:22:10 (Show Source):
You can put this solution on YOUR website!From the first equation:
z=1-x-2y
Put this into the second equation:
2x+3y+2(1-x-2y)=0
2x+3y+2-2x-4y=0
-y=-2
y=2
If y=2, put that in the third equation:
-x-3(2)+3(1-x-2(2))=1
-x-6+3-3x-12=1
-4x=16
x=-4
Now put y=2 and x=-4 into our z from step 1.
z=1-(-4)-2(2)=1
Giving solution set {-4,2,1}. This also can be solved through techniques of linear algebra (Cramer's Rule, RREF, etc). If you need it solved in a way such as that, send me an E-mail to enabla@gmail.com .
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Probability-and-statistics/160595: Please help! Homework question.
A person must score in the upper 2% of the population on an IQ test to qualify for membership in Mensa, the international high-IQ society. If IQ scores are normally distributed with a mean of 100 and a standard deviation of 15, what score must a person have to qualify for Mensa? 1 solutions
Answer 118414 by nabla(475) on 2008-10-06 09:50:31 (Show Source):
You can put this solution on YOUR website!First we standardize the score with
z=(x-u)/o
where z is the distance in standard deviations from the mean, x is the score to be standardized, u is the mean of the population, and o is the standard deviation of the population [or sample].
Now, we can suspect from a percentile rank chart that the upper 2% is 2 standard deviations from the mean. In fact, however there is approximately only 100-2.27=97.73 within two standard deviations above the mean. Chances are, however, that your instructor only wants 2 standard deviations above the mean:
z=(x-100)/15
15z+100=x
This gives a score, x, as a function of its distance from the mean[z]. So if we want 2 standard deviations above the mean, 15(2)+100=130. You will need an IQ of 130 to get into MENSA accordingly. Strictly speaking, the score would be a little higher than 130 (in order for to be ahead of 98% of the population) due to the reasoning above.
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Graphs/159919: Find the slope and the y-intercept.
f(x)= -3x-10
The slope is _____
The y-intercept is (0,__) 1 solutions
Answer 117989 by nabla(475) on 2008-10-02 15:37:12 (Show Source):
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Systems-of-equations/160013: Write an equation of the line containing the given point and perpendicular to the given line.
(3,5);6x+y=2
The equation of the line is y= ____ 1 solutions
Answer 117988 by nabla(475) on 2008-10-02 15:31:58 (Show Source):
You can put this solution on YOUR website![1] Find the slope of the given line:
y=-6x+2
gives m=-6=slope
[2] A perpendicular line will have slope -1/m. In this case, -1/m=1/6
[3] Apply point slope form y-y1=m(x-x1) with point (3,5)=(x1,y1).
y-5=(1/6)(x-3)
y=(1/6)x-1/2+10/2
y=(1/6)x+9/2.
Finished
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Linear-systems/159585: My problem asks me this:
Solve each system of linear equations.
y=x+2
y=2x
Do I use the xy chart to help work this problem and where do I go from there?
The problem has 2 variables and I don't know how to bring it down to one variable.
Please help me!! 1 solutions
Answer 117682 by nabla(475) on 2008-09-30 12:47:53 (Show Source):
You can put this solution on YOUR website!You can actually just subtract the first equation from the second in this case.
This gives:
0=x-2
2=x
And if x=2, y=4 by back substitution.
You could also solve by substitution, graphing, or other techniques from linear algebra (such as Cramer's Rule after some slight rearrangement).
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Numbers_Word_Problems/158838: The sum of three consecutive odd numbers is more than 375. Find the minimum values of these integers. 1 solutions
Answer 116994 by nabla(475) on 2008-09-25 00:32:08 (Show Source):
You can put this solution on YOUR website!3 consecutive odd numbers:
a
a+2
a+4
3a+6>375
3a>369
a>123
Now, if we want strictly more than 375, we will take a=125 to be our first odd number. This gives 125,127,129 as the numbers.
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Polynomials-and-rational-expressions/158850: I am thinking of three consecutive numbers. If I multiply the first with the second and then subtract three times the third the result is 57. What are the numbers? 1 solutions
Answer 116989 by nabla(475) on 2008-09-25 00:26:21 (Show Source):
You can put this solution on YOUR website!3 numbers:
a
a+1
a+2
words to symbols:
a(a+1)-3(a+2)=57
a^2+a-3a-6=57
a^2-2a-63=0
(a+7)(a-9)=0
so a=-7 or a=9. We want a to exist in the set of integers. Thus, we exclude a=-7 as a solution.
The numbers, then, are 9, 10, 11.
Check:
9(10)-3(11)=90-33=57
yes
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