SOLUTION: if sin 21 degree = x/y, then sec 21 degree - sin 69 degree is equal to ?

Algebra ->  Trigonometry-basics -> SOLUTION: if sin 21 degree = x/y, then sec 21 degree - sin 69 degree is equal to ?       Log On


   

Question 983552: if sin 21 degree = x/y, then sec 21 degree - sin 69 degree is equal to ?
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
if sin 21 degree = x/y, then sec 21 degree - sin 69 degree is equal to ?
------------

sec = 1/cos
sin(69) = cos(21)
=============
sec 21 degree - sin 69 degree
= 1/cos(21) - cos(21)
= (1 - cos^2(21))/cos(21)
= sin^2(21)/cos(21)
= %28x%5E2%2Fy%5E2%29%2F%28sqrt%28y%5E2-x%5E2%29%2Fy%29
= x%5E2%2F%28y%2Asqrt%28y%5E2-x%5E2%29%29
= x%5E2%2Asqrt%28y%5E2-x%5E2%29%2F%28y%2A%28y%5E2-x%5E2%29%29