NAME | RULE | DIAGRAM |
Complementary angles | Add to 90 degrees | ![]() |
Supplementary angles | Add to 180 degrees | ![]() |
(Hint to remember these: C in the alphabet and 90 when counting both come before S and 180.)
NAME | RULE | DIAGRAM |
Vertically opposite angles | Equal | ![]() |
NAME | RULE | DIAGRAM |
Corresponding angles | (F shape) | ![]() |
Co-interior angles | Add to 180 degrees (U shape) | ![]() |
Alternate angles | Equal (Z shape) | ![]() |
NAME | RULE | DIAGRAM |
Angle sum of triangle | Add to 180 degrees | ![]() |
Equilateral triangle | All angles equal 60 degrees | ![]() |
Isosceles triangle | Base angles are equal | ![]() |
Exterior angle of triangle | The exterior angle equals the sum of the two interior opposite angles. | ![]() |
To show that the angle sum of a triangle equals 180 degrees, draw a triangle, tear the angles and rearrange them into a straight line. Remember that the number of degrees in a straight line is 180 degrees.
Do a similar activity to show that the angles of a quadrilateral add to 360 degrees.
NAME | RULE | DIAGRAM |
Angle sum of quadrilateral | Add to 360 degrees | ![]() |
Opposite angles of parallelogram | Equal | ![]() |
NAME | RULE | DIAGRAM |
Radius meets tangent | The radius meets the tangent at right angles. | ![]() |
Angle at centre | The angle subtended at the centre of the circle is twice the angle at the circumference. (arrow shape) |
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Angle at circumference | Angles subtended by the same chord are equal. (butterfly shape) |
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Opposite angles of cyclic quadrilateral | Equal | ![]() |
Exterior angle of cyclic quadrilateral | The exterior angle of a cyclic quadrilateral is equal to the interior opposite angle. | ![]() |
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