1. Pythagoras Theorem

2. What is it?
If you know two sides of a right angled triangle you can work out the other side.
This is the right angle

3. How it works!
'The square on the hypotenuse is equal to the sum of the squares on the other two sides'
The hypotenuse is the longest side. It is always opposite the right angle. Which side is the hypotenuse in this diagram?

4. How to find the hypotenuse
The hypotenuse is a
a2 = b2 + c2

5. Worked Example QR2 = QP2 + PR2 QR2 = 42 + 72 QR2 = 16 + 49 QR2 = 65
QR = 8.06 cm (this is the longest side so it should be bigger than the other two sides)

6. Other types of questions
Is this triangle a right angled triangle?
If it is then Pythagoras should work
YZ should = 10
YZ2 =
YZ2 =
YZ2 = 106
YZ = 10.3 cm Is this triangle right angled?

7. Other questions
The farmer measured the red line to be 124metres. Is this field a perfect rectangle?
112m
50m
If it is then Pythagoras should work, because there are two right angled triangles in a square or rectangle.
H2 =
H2 = ,544
H2 = 15,044
H = m, Is this field a perfect rectangle?

8. Finding the smaller sides
Instead of adding, you take the smaller number away from the bigger one
YZ2 = 82 – 72
YZ2 = 64 – 49
YZ2 = 15
YZ = 3.9 cm

9. Tricky Questions Find the sloping side of this rubber;
35 mm
10 mm
10 mm
15 mm
50 mm
You have to find the right angled triangle and the two sides you need
H2 =
H2 =
H2 = 325
H = mm

10. Pythagorean Triples
These are three numbers that will fit into Pythagoras theorem e.g.
3, 4, 5
3² + 4² = 5²
= 25
Are these numbers 6, 8, 9 Pythagorean triples?
No, 100 does not equal 81