SOLUTION: If tan theta = 2 and sin theta < 0, what would the exact value of csc theta be? If you could show me the steps I need to take in order to solve this, that would be awesome. :D

Algebra ->  Trigonometry-basics -> SOLUTION: If tan theta = 2 and sin theta < 0, what would the exact value of csc theta be? If you could show me the steps I need to take in order to solve this, that would be awesome. :D      Log On


   



Question 832233: If tan theta = 2 and sin theta < 0, what would the exact value of csc theta be?
If you could show me the steps I need to take in order to solve this, that would be awesome. :D

Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
If tan%28theta%29+=+2 and sin%28theta%29+%3C+0, what would the exact value of csc%28theta%29 be?


The tangent is positive (since it's given as +2) and the sine is negative,
(since we are given sin%28theta%29%3C0. The tangent is positive in the
1st and 3rd quadrants, and the sine is negative in the 3rd and 4th, so
theta must be in the 3rd quadrant, or Q3.  So we draw an angle in
the 3rd quadrant like below.  Since the tangent is the opposite over the
adjacent, or y%2Fx, we make the given tangent, 2, into a fraction 2%2F1, but 
x goes left and y goes down, so they both have to be negative, so we
change the 2%2F1 to %28-2%29%2F%28-1%29 and make the numerator -2 be the value of y
and the denominator -1 be the value of x, so we have:    
 


Now we just need to know that the cosecant is the hypotenuse over the
opposite or r/y, which is %28sqrt%285%29%29%2F%28-2%29 or -sqrt%285%29%2F2. 

csc%28theta%29%22%22=%22%22%28-1%29%2Fsqrt%285%29 = %28-1sqrt%285%29%29%2F%28sqrt%285%29sqrt%285%29%29=-sqrt%285%29%2F5
 
Edwin