Find the real zeros of the trigonometric function on the interval 0 ≤ x

Question

Find the real zeros of the trigonometric function on the interval 0 ≤ x < 2π f(x)=2cos^2x+2sinx-3

solomonzelman · Answer

use    $\large\color{black}{ \bf  sin^2x+cos^2x=1   }$

parthkohli · Answer

$$f(x) = 2(1 - \sin^2 x) + 2\sin x - 3$$This is a quadratic in $\sin(x).$  For easy work, let $\sin(x)  = t$ and find the roots.

anonymous · Answer

So would it be sin = -1/2 and i look for those points on the unit circle>

parthkohli · Answer

No, I actually seem to be getting no values of sin from this.

anonymous · Answer

Im confused on how you got that, don't you distribute the 2 in front of the parenthesis and then set the equation equal to zero?

parthkohli · Answer

Yes.

I'm still getting no real solutions.

anonymous · Answer

Apparently I'm not doing something right then, this is how I've been solving the equation|dw:1401297237608:dw| and after that it doenst make sense.