00:01
We want to find the surface area of this hemispheres.
00:04
This is half of a sphere.
00:05
Our formula for surface area of a sphere is 4 pi r squared, but we only have half of one.
00:11
And surface area is what you can touch.
00:13
So when we're talking about a sphere, like a ball, we're talking about the outside edges of the ball.
00:19
So if i want to do a hemisphere, i'm going to take half of this formula.
00:29
But that just gets me the outside edge.
00:31
What you can touch, also touch on a hemisphere, is you can touch this bottom circle.
00:40
So that means i have to add a pi r square to it.
00:44
So before i plug anything in, we're going to simplify this formula...