Question

a. Use the formulas for lowering powers to rewrite the expression in terms of the first power of cosine:
(cos^4)x (or cos*x to the 4th power)

b.Use an appropriate Half- Angle Formula to Find the Exact value of the expression:
1. tan 15(Degrees)
2. cos 3pi/8(Radians)

Answer 1

cos^2 x = (1+cos2x)/2, so

cos^4 x = (1 + 2cos2x + cos^2 2x)/4
= (1 + 2cos2x + (1+cos4x)/2))/4
= (3 + 4cos2x + cos4x)/8

what do you get for the others?

Answer 2

1.square root 2 - 1 or 2^1/2 -1
2.I got -1/2 2^1/2-2^1/4 or -1/2 *square root 2 minus square root 2 (the second 2 has two square roots over it)