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area of rectangle

length x width

perimeter of rectangle

(length + width) x 2

area of parallelogram

base x height

area of triangle

(base x height) ÷ 2

perimeter of triangle

side 1 + side 2 + side 3

area of circle

3.14 x radius x radius

circumference of circle

3.14 x diameter (3.14 x 2 x radius)

area of a square

side x side

perimeter of a square

4 x side

Scalene

A triangle with NO congruent sides

Isosceles

A triangle with TWO OR MORE congruent sides

Equilateral

A triangle with THREE congruent sides

Acute

A triangle with THREE acute angles

Obtuse

A triangle with ONE obtuse angle

Right

A triangle with ONE right angle

Equiangular

A triangle with THREE congruent angles (they are all 60°)