Triangles
This section deals with 2D shapes and angles related to them. It might be worth looking at the National 4 Angles section before continuing.
For any triangle, the three angles add up to \(180^\circ\).
Example
Find the value of \(x^\circ\) in the triangle below.
Answer
\(x^\circ=180^\circ-(70^\circ+50^\circ)=180^\circ-120^\circ=60^\circ\)
An equilateral triangle is one with all three sides equal in length and all three angles equal to \(60^\circ\).
An isosceles triangle is one with two sides equal in length and two equal angles.
Question
In this diagram, the triangle is isosceles so both base angles equal \(70^\circ\).
What is the value of \(a^\circ\)?
\(a^\circ=180^\circ-(70^\circ+70^\circ)=180^\circ-140^\circ=40^\circ\)
More guides on this topic
- Determine the gradient of a straight line
- Circle geometry
- Calculating the volume of a standard solid
- Applying Pythagoras Theorem
- Using similarity
- Working with two-dimensional vectors
- Working with three-dimensional coordinates
- Using vector components
- Calculating the magnitude of a vector
- An Approximate History of Co-ordinates