Where do Area Formulas Come From?

Important Terms: Base and Height Base and height always make a right angle.

The Rectangle: A Basic Shape The Basic Grid: 12 units2 A = bh

The Parallelogram A = bh

The Triangle A = ½ bh

The Trapezoid

Summary Area of a rectangle = bh Area of a square = s2 Area of a triangle = ½ bh Area of a trapezoid = ½ h(base 1 + base 2)

Area of a Circle A =πr2

Easy Way to Memorize Circle Formulas Circumference Formula Area Formula C =πd A =πr2 “Cherry pie’s delicious, apple pies are too”

What are the area formulas for these shapes? The Semicircle The Quarter-Circle