# Solving trigonometric equations using sum and difference identities

### Solving trigonometric equations using sum and difference identities

#### Lessons

• 1.
Utilizing "Sum and Difference Identities" to solve:

a)
$\sin (x + {\pi \over 4} ) + \sin (x - {\pi \over 4} ) = -1,$
general solution in degrees

b)
$\cos 3x \cos x + \sin 3x \sin x =0,$
$0 \leq x$ < $2\pi$