Please help with this question!

Question

Two straight walls meet at an angle pi/4. A straight piece of fencing PQ of length 10 metres is used to create an enclosure APQ.

a) show that the area of APQ is given by 50(2^1/2)sin (3pi/4 - angle delta)
b) if the angle delta is varied, using differentiation or otherwise find the value of delta which maximizes the area of triangle APQ.

Thank you very much!

Answer 1

so what is "angle delta"?