# Angles – Acute, Obtuse, Straight and Right

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Lines AB and CD are parallel to one another (hence the » on the lines).
a and d are vertically opposite angles. Vertically opposite angles are equal. (b and c, e and h, f and g are also vertically opposite).
g and c are corresponding angles. Corresponding angles are equal. (h and d, f and b, e and a are also corresponding).
d and e are alternate angles. Alternate angles are equal. (c and f are also alternate). Alternate angles form a ‘Z’ shape and are sometimes called ‘Z angles’.
a and b are adjacent angles. Adjacent angles add up to 180 degrees. (d and c, c and a, d and b, f and e, e and g, h and g, h and f are also adjacent).
d and f are interior angles. These add up to 180 degrees (e and c are also interior).

Any two angles that add up to 180 degrees are known as supplementary angles.

The angles around a point add up to 360 degrees.
The angles in a triangle add up to 180 degrees.
The angles in a quadrilateral add up to 360 degrees.
The angles in a polygon (a shape with n sides) add up to 180(n – 2) degrees.
The exterior angles of any polygon add up to 360 degrees.