1. Pythagoras Theorem Hypotenuse NBc a b NB
To find the Hypotenuse we must square the other sides and then add together.
To find any other side we square the sides and subtract.
The side is then found by taking the square root.

2. Example
Find the length of PQ correct to 2 significant figures
21 m
15 m P R Q

3. Example
Find the value of y correct to 1 decimal place.
14.3 cm
3.7 cm y

4. Example
Calculate the value of x in each of the following (answers to 2dp)
(i) (ii)
15 cm
8 cm x
8 cm
15 cm x

5. Example
A ladder 17m long reaches 12m up a vertical wall. If it rests on horizontal ground, how far is its foot from the foot of the wall?

6. Exam past paper question: AQA 1994
Brian has a “2 in 1” ladder. He can use it either as a step ladder or as an extension ladder, as shown.
The ladder consists of two parts.
Each part is 240cm in length.
Each part is divided by five steps into six equal sections.
The length of AB = 198cm.
Calculate the height of the top of the step ladder from the ground.