Question

How do you solve `cosx (2sinx + 1) = 0`?

Answer 1

Solve: cos x(2sin x + 1) = 0

Explanation:

cos x(2sin x + 1) = 0
a. cos x = 0 --> `x = pi/2 and x = 3pi/2`

b. `sin x = - 1/2`. Trig table gives:
`x = - pi/6` or `(11pi)/6`.
Trig unit circle gives another arc `x = (7pi)/6` that has same sine value.

Finally, within interval `(0, 2pi)`, there are 4 answers:
`pi/2`; `(7pi)/6`, `(3pi)/2`; and `(11pi)/6.`