locus of point p will be x
2 + y
2 = 1 . a circle ( as

(sin
2 + cos
2) = 1 )
also we can find the equation of the line which forms the triangle with the x and y axes...
y -

(3/2) = (

(3/2) - 0 ) / ( 0 -

(3/2) ) X (x - 0)
y = -x +

(3/2)
find points of intersection....
as y is cos

and x is sin

acc. to question therefore
solving,
divide both sides by

2 and use formula of sin( a + b)
we get sin( pi/4 +

) =

3 / 2

= pi / 12 , 5 pi / 12 for 1st quadrant as the triangle is there
thus, point p will be ON the triangle for these values of

and also for

= 0 and pi/2 as at these values sin gives x axis and y axis which r the other 2 sides of the triangle.
thus

E ( 0 , pi/12) U ( 5 pi/12 , pi /2)
PS. check it out by drawing also . my point will become clear to you
plz rate me. :)