 So in this video, we're going to look at the proof of the area of triangles equals a half AB sine C formula. We have this triangle with vertices A, B and C, sides A, B and C, and vertical height H. Using the area of a triangle equals a half base times height, this means the area is a half AH. But there isn't an H in the other formula, so we need to get rid of the H from this one. Using Socoteura, where C is our angle, H is the opposite and B is the hypotenuse, we can say that sine C equals H over B. And rearranging, we can get H equals B multiplied by sine C. We can now substitute this into our area equals a half AH to replace the H. And there we have our formula.