The angles in a triangle are in the ratio 1:2:3. Show that the triangle is a right - angled triangle.

Angles in a triangles add up to 180°

Respectively 1 : 2 : 3 is going to be 1 x, 2 x and 3 x so,

1 x + 2 x + 3 x = 180°

⇒ Simplify

6 x = 180°

⇒ Divide by 6 on both sides to isolate x

x = 30°

Since the ratio was 1 x : 2 x : 3 x and x is 30°,

30 : 60 : 90

And since there is a 90° angle, it is a right - angled triangle