Calculate area, perimeter, height and angles of an isosceles triangle from its equal sides and base.
An isosceles triangle has two equal sides (legs). The height is found using the Pythagorean theorem on the half-base and leg. Base angles are equal and found via inverse cosine.
Height
h = √(leg² − (base/2)²)
Area
A = ½ × base × height
If you know the base angle θ and the leg, the base = 2 × leg × cos(θ). Enter those values to get all properties.
Yes. If base > leg × √2, the apex angle exceeds 90°.