The Cosine Rule

Abccba cos2222

Draw any triangle.

Measure sides and angles.

Test this rule out!

Angle A is opposite side a. Angle B is opposite side b. Angle C is opposite side

c.

Your objective is to prove the Cosine Rule!

On your worksheet there are eight statements/diagrams – these are the key elements of your proof.

Your task is to use the elements to create a proof of the Cosine Rule.

You should explain each step of your proof.

You may create elements of your own.

You may choose not to use some of the elements.

Create a poster of your proof!

Abccba cos2222

222 )( hxca 2222 2 hxcxca 222 xbh

22222 2 xbxcxca

Abx cos

cxcba 2222

Abccba cos2222