Area under a curve How could one determine the area between the unit circle and $y = x \tan b$ where $b$ is some constant in $[0, \pi/2)$
I am confused as to how the $b$ plays a factor in this. 

If we consider a line $y=mx$ and the unit circle, the line , regardless of the slope divides the circle in 2. If what you want is the area above the line, Area $= \dfrac{\pi}{2}$ If you want the area between the line $y=0 $ and the line $y=mx$ in the circle, notice that this area is  a sector with angle $\tan^{-1}m=b$ and so has area $\dfrac{b}{2}$
