Trigonometrymedium · Past Paper
If sin A + cos A = m, then sin 2A is:
Am²
Bm² - 1
Cm² + 1
D2m
✓ Correct Answer: B — m² - 1
Squaring both sides: sin² A + cos² A + 2 sin A cos A = m². So 1 + sin 2A = m², meaning sin 2A = m² - 1.
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