The Isosceles Triangle

Mathematics — Second Preparatory

Common mistakes

Forgetting that the base angles are equal, so the required value is found in a wrong way.
Dividing 180° by 3 to find a base angle. The correct method is to subtract the vertex angle from 180° and then divide by 2.
Treating the base as one of the legs, which gives a wrong perimeter equation.
Confusing the altitude with the median drawn from the vertex. They coincide only in an isosceles triangle, so this is a special case, not a general rule.

The Isosceles Triangle · 4 / 5