Solving trigonometric equations using sum and difference identities

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Now Playing:Solve trig equations using sum and difference identities – Example 1a

Utilizing "Sum and Difference Identities" to solve:
1. $\sin (x + {\pi \over 4} ) + \sin (x - {\pi \over 4} ) = -1,$
  general solution in degrees
2. $\cos 3x \cos x + \sin 3x \sin x =0,$
  $0 \leq x$ < $2\pi$

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