burkinaval1b

2022-01-16

Prove the identity.
$\mathrm{sin}4x=2\mathrm{sin}2x\mathrm{cos}2x$

zurilomk4

Expert

Work on the left side.
Write 4x as 2*2x:
$\mathrm{sin}4x=\mathrm{sin}\left(2\cdot 2x\right)$
Use the double-angle identity for sine $\mathrm{sin}2u=2\mathrm{sin}u\mathrm{cos}u$ where u=2x:
$\mathrm{sin}4x=2\mathrm{sin}2x\mathrm{cos}2x$
Result:
Hint: Write 4x as 2*2x and use the double-angle identity for sine.

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