Question

Find the range of y=3/2cos4x-1

Answer 1

Range = [- 2.5, 0.5] = [ - 5/2, 1/2]

Explanation:

Smallest value of cos α = - 1,

largest value of cos α = 1.

When cos 4x = - 1, y=3/2cos4x-1 = 3/2*(-1) - 1 = - 5/2 = - 2 1/2 = - 2.5

When cos 4x = 1, y=3/2cos4x-1 = 3/2*1 - 1 = 1/2 = 0.5

Range = [- 2.5, 0.5] = [ - 5/2, 1/2]