Calculate the area and height of an isosceles triangle from its two equal sides and base. Includes triangle validity checking and a worked example.
An isosceles triangle has two equal sides.
When the altitude is drawn from the vertex between the equal sides, it bisects the base.
The height is found from the equal side and half the base, then area is one half base times height.
| Equal Side | 5 cm |
| Base | 6 cm |
| Triangle Area | 12 |
| Height | 4 |
| Valid Triangle | 1 |
The height is 4 cm and the area is 12 square centimetres.
Try this example →If a is the equal side and b is the base, area is b times the square root of a squared minus b squared divided by 4, all divided by 2.
The altitude of an isosceles triangle bisects the base into two equal halves.
No. The base is the third side, opposite the vertex between the equal sides.
The height is 4 cm and the area is 12 square centimetres.