I'm so confused rite now. The question is: find the altitude of an isoceles triangle whose base is 10 and whose congruent sides are 9.

Someone please explain!:confused:

Just use Pythagoras. Drop a perpendicular from the top to the midpoint of the base.

Then the width of that midpoint is 5 and the hypoteneuse is 9

h=\sqrt{9^{2}-5^{2}}