Rewrite the equation by using the definition of the tangent function:

Since there is a cosine at the denominator, it can't be zero. So, we know that

With this restriciton, let's multiply the whole equation by cos(x):

We don't like having sine and cosine in the same equation. We can fix this by using the fundamental identity of trigonometry to express cos^2 in terms of sin^2:

The equation becomes

which you can rearrange as

This is a quadratic equation is sin(x): if you let t=sin(x) the equation becomes

which yields solutions

Now, remember that t is sin(x), and as such it can't exceed the interval [-1,1]. Since the second solution is greater than 1, we can only accept the first solution. So, we have
