Question

Sin ² (θ) - cos² (θ) = 2 sin² (θ) -1

Answer 1

The equation is not true.

Explanation:

Starting with the left side,

sin²(θ) - cos²(θ) = 1 - cos²(θ) - cos²(θ) = 1 - 2cos²(θ)

The right side,

2 sin²(θ) - 1 = 2(sin²(θ) - 0.5)

Thus, in general, sin²(θ) - cos²(θ) ≠ 2 sin²(θ) -1.