RIGHT TRIANGLESSolution of a right triangle when two sides are known

Right angle

Triangle

A shape with 3 sides

Theorem

A mathematical formula for calculating values.

Side

Length

The measurement of the extent of something along its greatest dimension

Hypotenuse

“X square”

“Plus”

“Equal”

“Square root”

Procedure

If the length of two sides in a right-

angled triangle is known, then the

length of the third side can be

calculated using Pythagoras’ Theorem.

The first thing that we need to do is to check whether we can use Pythagoras’ Theorem or not.

Does the triangle have right angle?

Yes, it does

Are we given enough information?

Since we are looking for a side, do we have the length of the other two sides?

Yes, we do.

This rule states that the square on the hypotenuse (what we are looking for) is equal to the sum of the squares on the other two sides, or what we get when we square the other two lengths and add them together.

Using Pythagoras’ Theorem, we get:

Practice:

Say which of the following triangles is really right-angled:

A) B) C)

Find the length of the missing side

A) 10 cm B) 7 cm C) 8 cm

SUMMARY