Trigonometry Homework #11 due 5-18

Prove each identity.

  1. \cos^4\theta-\sin^4\theta=\cos(2\theta)
  2. \sin(4x)=4\sin{x}\cos{x}\cos(2x)
  3. \frac{\sin(2x)}{1+\cos(2x)}=\tan{x}
  4. \cot\alpha+\tan\alpha=2\csc(2\alpha)
  5. \tan(\pi-\alpha)=-\tan{\alpha}
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