Altitude of a Triangle is a line through a vertex which is perpendicular to a base line. The length of the altitude is the distance between the base and the vertex. Two congruent triangles are formed, when the altitude is drawn in an isosceles triangle. The altitude to the base of an isosceles triangle bisects the vertex angle. Here is a simple online altitude of an Isosceles triangle calculator to find its altitude from its base length and side length.
An Isosceles triangle with base length of 9 cm and side length of 12 cm. Find its altitude.
Altitude of an Isosceles Triangle = 9 x √(4 x 122 - 92 ) / 2 x 12
= 8.3432 cm