Angle Facts: Points, Lines and Parallel Lines

Basic angle facts

1. Angles at a point: Add up to 360°.

2. Angles on a straight line: Add up to 180°.

3. Vertically opposite angles: Are equal.

Parallel lines

When a transversal cuts parallel lines:

Corresponding angles are equal. (F-shape)

Alternate angles are equal. (Z-shape)

Co-interior/Allied angles add to 180°. (C-shape)

Note: Always give a reason when solving: 'angles on a straight line', 'alt ∠ s, AB||CD'.

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