Lesson 2 Module 5 Gr. 6 EngageNY

Three-sided polygon

one interior angle must measure exactly  $90\degree$  

The formula for a rectangle is length x height.

So the formula for the area of a right triangle is 

 $A=\ \frac{b\cdot h}{2}$  also written as  $A=\frac{1}{2}\ b\cdot h$  

(multiply by 1/2 is the same as divide by 2)

because we know that right triangle is 1/2 of the rectangle we can use the formula for the rectangle (length x width) and divide it by 2 ( or multiply by 1/2).

because the sides form a right triangle are perpendicular, they form the right angle, so it doesn't matter which of these two sides is labeled the base and which is labeled the height.

the commutative property of multiplication allows us to calculate the formula in any order.

How are the formulas of rectangles and right triangles related?

When the two sides that form the right angle are the same length in both a rectangle and a right triangle, the area of the right triangle is exactly half of the area of the rectangle.

Therefore, the area of the rectangle divided by 2 (or multiplied by half) is equal to the area formula of the right triangle.