Slant Height First

If a pyramid is given by its base edge and its true height, the surface area still needs the slant height. Find it from the right triangle inside, then use the surface rule.

This is the pyramid from the last lesson, given by its height 4 instead. Half the base is 3, so ${s}^{2} = {4}^{2}+{3}^{2} = 25$ and s = 5. Then the surface area is ${6}^{2}+2\cdot 6\cdot 5 = 96$, as before.

On the board: tap the slant height and pick Slant height, then tap the pyramid and pick Surface area of a pyramid.