Let us transfer into the right-hand side of the equation and calculate the sine of the both sides of the resulting equation

[using

Squaring both sides, we get

whose roots are and .

Let us verify

Substituting in the given equation, we get

Thus, is the root of given equation. But, when substituting in Eq. (i), we get

i.e. of Eq. (i).

Hence, is a root of the given equation as it satisfies both given and Eq(i).

──────────────────────────────────────────────────────────────────────────────────────────