SOLUTION: Find the value of sec(theta) if tan(theta)= Negative square root of 114 divided by 19 and sin(theta)>0.

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Question 840926: Find the value of sec(theta) if tan(theta)= Negative square root of 114 divided by 19 and sin(theta)>0.
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
Find the value of sec(θ) if tan(θ)= -sqrt%28114%29%2F19 and sin(θ)>0.
There are two ways to do this problem.  We'll do it both ways:

First way.  θ is in quadrant II because that 
is the only quadrant in which the tangent 
is a negative number and the sine is a 
positive number.

So we draw the angle θ in quadrant II.
The tangent = %28opposite%29%2F%28adjacent%29 = y%2Fx. So
we take the numerator of the tangent %22%22%2Bsqrt%28114%29 as y, 
(we take it positive because it goes up from the x-axis).
And we take the denominator of the tangent -19 as x, 
(we take it negative because it goes left from the origin).

We use the Pythagorean theorem: hypotenuse%5E2=adjacent%5E2%2Bopposite%5E2
or rē = xē + yē
   rē = 19ē + %28sqrt%28114%29%29%5E2
   rē = 361 + 114
   rē = 475
    r = sqrt%28475%29 = sqrt%2825%2A19%29 = 5sqrt%2819%29

(r is always taken positive).



And since we know that the secant = hypotenuse%2Fadjacent = r%2Fx,

sec(θ) = %285sqrt%2819%29%29%2F%28-19%29 = -5sqrt%2819%29%2F19

--------------------------------

Second way:

Use the identity: 

1 + tanē(θ) = secē(θ)
1 + %28-sqrt%28114%29%2F19%29%5E2 = secē(θ)
1 + 114%2F361 = secē(θ)
361%2F361 + 114%2F361 = secē(θ)
475%2F361 = secē(θ)
%22%22+%2B-+sqrt%28475%2F361%29 = sec(θ)
%22%22+%2B-+sqrt%28475%29%2Fsqrt%28361%29 = sec(θ) 
%22%22+%2B-+sqrt%2825%2A19%29%2F19 = sec(θ)
%22%22+%2B-+5sqrt%2819%29%2F19 = sec(θ)

We have to decide which quadrant θ is in just
as we did using the first method.  So the secant
in QII is negative, so the answer is

-+5sqrt%2819%29%2F19 = sec(θ)

You can do the problem either way.

Edwin