Triangles
A triangle has three sides and three angles. The three angles always add up to 180°.
Perimeter = side 1 + side 2 + side 3
Area = base × height ÷ 2
Example
Base 8 cm, height 5 cm. Area = 8 × 5 ÷ 2 = 20 cm²
Third angle = 180° − (first angle + second angle)
Example
Angles 50° and 60°. Third angle = 180° − (50° + 60°) = 70°