A sector of a circle of radius "r" cm has an area of "A"cm². Express the perimeter of the sector in terms of "r" and "A"
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First, split the triangle into half.
So the angle 38 becomes 38/2=19.
So we know two angles in the triangle:
One is 19 degrees.
The other one is 90 degrees (marked red).
The angles in a right-angled triangle add up to 180 degrees.
So to find the x angle, we calculate it by:
180 - (90+19) = 71
(the sum of three angles) - (the sum of the two known angles) = unknown angle
So x = 71 degrees.
