Question

why is sin0 =0, and cos0=1?

Answer 1

c$Cos^{2}C = 1- Sin^{2}C \\ CosC = \sqrt{1- Sin^{2}C } \\ Cos0 = \sqrt{1-sin^{2}0 } \\ Cos0 = \sqrt{1-0} = \sqrt{1} =1$

2nd method see in the attachment