The complete set of real values of 'a' such that the point lies triangle `p(a, sin a)` lies inside the triangle formed by the lines `x-2y +2= 0; x+y=0` and `x-y-pi=0`

Explanation

In the figure, triangle OAB is formed by line y=x, x+y=4 and x-axis.
Variable point (3a,a) lies on the line x =3y for all real values of a.
Line x=3y meets the line x+y-4=0 at P (3,1).
Hence, point (3a,a) must lie between O and P on line 3x=y.
`therefore 0 lt a lt 1`