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Angles in the same segment - Higher

The angles at the by the same arc are equal.

Put more simply, angles in the same segment are equal.

Angles \(a = a\)

Circle with identical angles, a, at the circumference

Example

Calculate the angles \(p\) and \(q\).

Circle with angles, 52degrees, 40degrees, p and q at the circumference

Angles in the same segment are equal.

\(p = 52^\circ\)

\(q = 40^\circ\)

Proof

Let the obtuse angle MOQ = \(2x\).

Circle with double angle (2x) at centre

Using the circle theorem, the angle at the centre is twice the angle at the circumference.

Angle MNQ = \(x\) and angle MPQ = \(x\).

Two angles (x) at circumference

Therefore angle MNQ = angle MPQ.