And if angles 𝑥, 𝑦 and 𝑐 equal 180, our second rule. Then angles 𝑎, 𝑏 and 𝑐 must equal 180 as well. This proves that the angles of a triangle must add up to 180 degrees.

For a right-angled triangle, follow these steps to calculate the length of a side, \(x\), when another side and an angle Ɵ is given: Formula triangles can be used to help with rearranging the ...