How can we derive the double-angle formulas for sine and cosine and use them to solve complex trigonometric equations?

Answer 1

Steven Garcia

To derive the double-angle formulas for sine and cosine, we start with the angle addition formulas: sin(2θ) = 2sin(θ)cos(θ) and cos(2θ) = cos²(θ) – sin²(θ). These formulas can simplify complex trigonometric equations by reducing the number of terms and making it easier to solve for unknown variables.