Edexcel IGCSE Maths 复习笔记 4.8.1 Pythagoras Theorem

What is Pythagoras?

• Pythagoras was a Greek mathematician who lived over 2500 years ago
• He is most famous for Pythagoras’ Theorem, which includes the important formula for right-angled triangles

Pythagoras' theorem?

• The longest side in a right-angled triangle is called the hypotenuse – this will always be the side opposite the right angle
• If we label the hypotenuse c, and label the other two sides a and b:

then Pythagoras’ Theorem tells us that:

a² + b² = c²

(where a, b, and c are the lengths of the three sides) 

Using Pythagoras’ theorem

• To find the length of the hypotenuse use:c = √a² + b²

  (Note that when finding the hypotenuse you add inside the square root)

• To find the length of one of the other sides use: 

  a = √c² – b² or b = √c² – a²Note that when finding one of the other sides you subtract inside the square root