Step-by-step explanation:
Firstly, notice that this shape is composed of ³/₄ of a circle and ¹/₂ of a square;
The lower left part is the ¹/₂ square, with only 2 sides (a left and lower side) of length 3 units;
The perimeter of this part of the shape is simply the sum of the two sides:
3 + 3 = 6
The remaining part is the ³/₄ circle, which has a radius of 3 units;
The circumference of a circle is found by the formula:
πd
d = diameter = 2 × radius
We only have ³/₄ of the circle, however, so we only have ³/₄ the circumference:
³/₄ × π(2(3)) = ³/₄ × 6π
= ⁹/₂π (or, equally, 4.5π)
So the total perimeter is the sum of the perimeter of the ¹/₂ square and the ³/₄ circle:
4.5π + 6
. Does 
? If it does, you have yourself a right triangle. If it doesn't, then it isn't a right triangle.
