Equilateral

All the sides are the same length and all the angles are equal.

Isosceles

Two sides are of the same length and two angles are of equal size.

Scalene

All sides are different lengths and all the angles are of different sizes.

Acute angle

A triangle with three acute angles, each less than 90°.

Right angle

A triangle containing one right angle (90°).

Obtuse angle

A triangle containing one obtuse angle (over 90°).

Square

All the sides are the same length and all the angles are right angles.

Rectangle

Opposite sides are the same length and all angles are right angles.

Rhombus

All sides are the same length but none of the angles are right ngles.

Parallelogram

Opposite sides are parallel to each other and of the same length.

Trapezium

One pair of the opposite sides is parallel.

Kite

Adjacent sides are equal length and the diagonals intersect at right angles.

Shape

Circumference

Area

circle

2¹r

¹r2

Parallelogram (l = length, h = perpendicular distance to side parallel to l)

lh

Rectangle (l = length, w = width)

lw

triangle

1/2lh

Shape

Volume

Surface area

Cone (h = perpendicular height)

1/3¹r2h

¹r2+¹rl

cylinder

¹r2h

¹r2+2¹rh

Pyramid (B = area of base)

1/3Bh

sphere

4/3¹r3

4¹r2