Scratch this, I managed to figure it out. I forgot that cos is the x value and sin is the y value on the Cartesian Plane
For the following value of , determine the radian value of
a) -1/2
First I found y from the equation
y= +- \sqrt{y}
My graph therefore is in the 1 and 2 quadrant due to y having + and - values
then i found inverse cos^-1 (1/2) = 1.05
so: pi - 1.05 or 1.05
However the answer according to the book is (4pi)/3