Understanding Triangle Areas: Key Revision Notes

Types of Triangles

Every triangle you'll ever encounter has one thing in common: all three angles add up to 180 degrees. This is a fundamental rule that never changes, no matter what type of triangle you're working with.

There are three main types of triangles you need to know. An equilateral triangle is the most symmetrical - all three sides are exactly the same length, and all three angles are 60 degrees each.

A scalene triangle is like the rebel of the triangle family - every side is a different length, and every angle is different too. Most triangles you see in real life are scalene triangles.

Isosceles triangles are the compromise between the two - they have exactly two equal sides and two equal angles, with the third side and angle being different.

Quick Check: Remember that no matter which type you're dealing with, those three angles will always add up to 180 degrees!

Finding the Area of Triangles

Here's the brilliant news: there's just one formula for finding the area of any triangle, regardless of whether it's equilateral, scalene, or isosceles. The triangle area formula is: Area = ½ × base × height.

You can write this formula in different ways - some people prefer base × height ÷ 2, which gives exactly the same answer. The key is identifying your base (any side of the triangle) and the height (the perpendicular distance from that base to the opposite corner).

The height is crucial - it must be measured at a right angle to the base you've chosen. Don't just use any side length as the height, as this will give you the wrong answer.

Top Tip: Always double-check that your height measurement forms a 90-degree angle with your chosen base - this is where most mistakes happen!