Let S = {$$\theta $$ $$ \in $$ [–2$$\pi $$, 2$$\pi $$] : 2cos²$$\theta $$ + 3sin$$\theta $$ = 0}. Then the sum of the elements of S is

The sum of all values of $$\theta $$ $$ \in $$$$\left( {0,{\pi \over 2}} \right)$$ satisfying
sin² 2$$\theta $$ + cos⁴ 2$$\theta $$ = $${3 \over 4}$$ is -

If  0 $$ \le $$ x < $${\pi \over 2}$$,  then the number of values of x for which sin x $$-$$ sin 2x + sin 3x = 0, is :

If sum of all the solutions of the equation

$$8\cos x.\left( {\cos \left( {{\pi \over 6} + x} \right).\cos \left( {{\pi \over 6} - x} \right) - {1 \over 2}} \right) = 1$$

in [0, $$\pi $$] is k$$\pi $$, then k is equal to