Geometry Theorems

When angles meet on a straight line

Angles add to 180°

When angles meet at a point

Angles add to 360°

When angles that meet form cross

Opposite angles are equal and add to 360°

When line passes through parallel lines

Corresponding angles are equal

Alternate angles are equal

Interior angles add to 180°

Equilateral triangle

• 3 sides equal

• 3 interior angles are equal (60°)

Isosceles triangle

• 2 sides are equal

• Base angles are equal

Right-angled triangle

• 1 angle of 90°

• Pythagoras can be applied

Scalene

No equal angles or sides

Congruent triangles

• Three pairs of sides are equal (SSS)

• Two pairs of sides are equal and the angles between them are equal (SAS)

• Two pairs of angles are equal and sides between them are equal (ASA)

• Both triangles have right angle and hypotenuses are equal and one pair of corresponding sides are equal (RHS)

Axiom

Statement acepted without proof

Theorem

Statement that can be shown to be true through the use of axioms and logical argument

Corollary

Statement attached to a theorem which has been proven and follows obviously from it