About the isosceles triangle calculator
An isosceles triangle has two equal legs, so its two base angles are equal too. The height from the apex bisects the base, splitting the shape into two mirror-image right triangles, which is how every formula here is derived.
Formulas
| Height | h = √(a² − b²/4) |
| Area | K = bh/2 |
| Base angle | α = acos(b/2a) |
| Apex angle | β = 180° − 2α |
Frequently asked questions
How do I find the height of an isosceles triangle?
h = √(a² − (b/2)²), where a is a leg and b the base.
How are the angles related?
The two base angles are equal and the apex angle is 180° − 2α.