area between markers and curve

[MM_10735997]

I've shaded a portion between markers and curve as one portion as a other as b, how can i find area between them.

[Werner_E]

Maybe that way

Keep in mind that the "area" is of dimension length times angle. Probably you are interested in the value with meter times degree.

Prime 9 worksheet attached

[ttokoro · Accepted solution]

[MM_10735997]

can i know the function of the shaded portion 

[ttokoro]