Question

How do you solve `cos2xsinx+sinx=0` in the interval [0,360]?

Answer 1

`0, pi/2, pi, 2pi`

Explanation:

cos 2x.sin x + sin x = 0
sin x(cos 2x + 1) = 0
Solve this equation for x.
a. sin x = 0 --> `x = 0, x = pi, and x = 2pi`
b. cos 2x = 1 = 0
cos 2x = -1
`cos 2x = cos pi`
`2x = pi`
`x = pi/2`
Answers for `(0, 2pi)`:
`0, pi/2, pi, 2pi`