Deduction (Year 9)

Alternate angles: When two lines are crossed by another line (the Transversal), a pair of angles on the inner side of each of those two lines but on opposite sides of the transversal.

Corresponding angles: When two lines are crossed by another line (the Transversal) 

Parallel lines: Two lines that never meet. They are always the same distance apart with the same gradient 

Perpendicular lines: Two lines that meet at a right angle 

Isosceles triangle: A triangle with two equal sides.

Equilateral triangle: A triangle with all three sides of equal length. All the angles are 60° .

Polygon: A two-dimensional with straight sides.

Interior Angle: An angles inside a shape, between two joined sides. 

Conjecture: a statement that might be true but is not proven.

Counterexample: an example that disproves a statement