(a) The integral is equal to the area of the triangle; it has height 20 and base 10, so the area is 20*10/2 = 100.
(b) The integral is equal to the area of the semicircle with radius 10. It's also under the horizontal axis, so the area is negative. The semicircle has area
, so the integral is -50π.
(c) First compute

which is the area of the triangle on the right. It has height and base 5, so its area is 25/2.
Then split up the desired integral as

and plug in the integral values you know:

Since you said angle, I assume you mean a triangle, so:
Take the number of the angles you have and add them, then, subtract it by 180. It gives you the missing angle of your triangle!
Answer:
0.5 or 1/2
Step-by-step explanation
I dont know if they want the answer in fraction form.