Whats the area of a shaded circle with 90 degree angle?

Answer 1

The area inside a full circle is given by the formula: Area = Pi x r x r where r is the length of the circle's radius.

However, the angle of 90 degrees is only one quarter of a rotation of a line about a point at its end, so the required area is one quarter of the full area.

So the required area is (Pi x r x r) divided by 4

A fairly accurate answer is found if we use the value 3.14 for Pi

It is interesting that the number Pi cannot be written down exactly as a fraction or a decimal. It is called an "irrational" number.