Polygons are multi-sided shapes with different properties. Shapes have symmetrical properties and some can tessellate.

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Angles around a point add up to 360°. This fact can be used to calculate missing angles.

Calculate angle \(a\).

\[a = 360^\circ - 60^\circ - 95^\circ - 105^\circ = 100^\circ\]

Angles on a straight line add up to 180°. This fact can also be used to calculate angles.

Calculate the angles \(b\) and \(c\).

\[b = 180^\circ - 30^\circ = 150^\circ\]

\[c = 180^\circ - 150^\circ = 30^\circ\]

\(c\) and \(30^\circ\) are called vertically opposite angles.

Vertically opposite angles are equal.