7.3 Double-Angle, Half-Angle, and Product-Sum Formulas
Ideas in this lesson
- Double-angle formulas
- Power-reducing formulas
- Half-angle formulas
- Product-to-sum and sum-to-product
Double-angle formulas · Worked example
sin x = \frac{1}{3}, cos x = \frac{2√2}{3}. sin 2x?
Answer: \frac{4√2}{9}
2 · \frac{1}{3} · \frac{2√2}{3}.