There are plenty of ways to find the height of an isosceles triangle. It all depends on the imformation you have been given about the triangle in the question.
You can use basic trigonometry -> SOHCAHTOA
You can also use sin or cos rules -> C2 = A2 + B2 - 2ABcos(angle)
What makes isosceles special is the fact that two of its angle are the same so if you know just one of the angles in triangle you can work out the other two angles. (bear in mind that the total internal angle of a triangle is 180 degrees).
hope it explains your question.
