Double Angle Formulas/Sine/Proof 2
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Theorem
- $\sin 2 \theta = 2 \sin \theta \cos \theta$
Proof
| \(\ds \sin 2 \theta\) | \(=\) | \(\ds \map \sin {\theta + \theta}\) | ||||||||||||
| \(\ds \) | \(=\) | \(\ds \sin \theta \cos \theta + \cos \theta \sin \theta\) | Sine of Sum | |||||||||||
| \(\ds \) | \(=\) | \(\ds 2 \sin \theta \cos \theta\) |
$\blacksquare$
Sources
- 1953: L. Harwood Clarke: A Note Book in Pure Mathematics ... (previous) ... (next): $\text V$. Trigonometry: The addition formulae