SOLUTION: Using a double-angle or half-angle formula to simplify the given expressions. if cos^2(25∘)−sin^2(25∘)=cos(A∘) then A= . If cos^2(9x)−sin^2(9x)=cos(B) then B=

Algebra ->  Trigonometry-basics -> SOLUTION: Using a double-angle or half-angle formula to simplify the given expressions. if cos^2(25∘)−sin^2(25∘)=cos(A∘) then A= . If cos^2(9x)−sin^2(9x)=cos(B) then B=      Log On


   

Question 1170546: Using a double-angle or half-angle formula to simplify the given expressions.
if cos^2(25∘)−sin^2(25∘)=cos(A∘) then A= . If cos^2(9x)−sin^2(9x)=cos(B) then B= . I have tried cos(50) for cos^2(25 deg)-sin^2(25deg)=cos (A deg).

Answer by greenestamps(13216) About Me  (Show Source):
You can put this solution on YOUR website!


The double angle formula is

cos%28x%29%5E2-sin%28x%29%5E2+=+cos%282x%29

So

cos%2825%29%5E2-sin%2825%29%5E2+=+cos%2850%29

cos%289x%29%5E2-sin%289x%29%5E2+=+cos%2818x%29