Solve the equation on the interval [0, 2π). Suppose f(x) = cos θ - 1. Solve f(x) = 0.

Answer 1

Hello Evora,

This should be a straight forward approach. Have a unit-circle handy!

f(x) = Cos(θ) -1 = 0

Cos(θ) = 1. On the interval of [0,2π), where does Cosine =1? Remember, 2π is not in the range of [0,2π).

Remember, Cosine(θ) has a period of 2π, and at 0 radians, Cosine = 1. It will not equal 1 again until 2π radians later. Since 2π is not in the interval, the only answer is θ = 0 radians.