Circle Geometry Essentials

Front

Angle at Centre

Back

Twice angle at circumference

Front

Angle in Half Circle

Back

90 degrees

Front

Angles in Same Segment

Back

Equal

Front

Cyclic Quadrilateral

Back

Opposite angles sum to 180°

Front

Tangent to Circle

Back

Perpendicular to radius

Front

Radius and Tangent

Back

Meet at 90°

Front

Angle Subtended by Arc

Back

Same at circumference

Front

Tan Chord Theorem

Back

Angle between tangent and chord = the angle in the opposite segment at the circumference

Front

Chord Bisector

Back

Passes through circle's center

Front

Equal Chords

Back

Equal angles at center