Area of Triangles

Area of Triangles

A triangle with the same base and perpendicular height as a rectangle covers half the rectangle. That is why $A=\tfrac12 bh$. The height must be at a right angle to the chosen base; it is not necessarily a sloping side. Include square units in the final answer.

Worked example

A triangle has base 12 cm and perpendicular height 7 cm. $A=\tfrac12(12)(7)=42\text{ cm}^2$.

Exam method

1. Choose a base. 2. Find the perpendicular height. 3. Multiply base by height, halve it, and attach square units.