4 pts Using a doubleangle or halfangle formula to simplify t

(4 pts) Using a double-angle or half-angle formula to simplify the given expressions. (a) If cos2 23° - sin 23°- cos A°, then (b) If cos-4x-sin-4x = cos B, then ees

Solution

a. cos²23 -sin²23

This is of the form cos²A-sin²A which is equal to cos(2A)

so we get cos(2*23)=cos 46 degree

So A=46

b. cos ²4x-sin²4x

cos(2*4x)=cos (8x)

B=8x