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Remember that the interior angles of a triangle add up to 180º.

 

right-angled triangle has one 90º angle.

An isosceles triangle has two equal angles.

An equilateral triangle has three equal angles, each of size 60º

 

Example

Two of the angles in a triangle are 35º and 110º.  Which type of triangle is it?

 

Answer

We must first work out the third angle which will be:

180º - (35º + 110º) = 180º - 145º = 35º

 

So the triangle has angles 35º , 110º, 35º 

 

Two angles are equal so it is isosceles.

 

10 questions