Urgent, Trigonometric function and graph

A circle is divided by a chord into two segments such that the areas of the segments are in the ratio 3:1 . If the chord subtends an angle of $\displaystyle 2{\theta}$ at the centre , where $\displaystyle {\theta}$ is acute , show that if the angle is measured in degress and if $\displaystyle {\phi}={2\theta - 90}$ , then $\displaystyle {cos \phi} = {(\pi\phi)/180}$

By drawing the graphs of $\displaystyle {cos \phi}$ and $\displaystyle {(\pi\theta)/180}$ for values of $\displaystyle {\phi}$ between 30degree and 50degree, estimate the value of $\displaystyle {\phi}$ to the nearest half degree, that satisfies the above equation. Then obtain an approximation of the value of $\displaystyle {\theta}$

I would be grateful if you can help me with the picture of the circle, thanks. I just can't envisage that.

Thanks in advance.