If A+B+C=90° then prove that #sin^2 (A/2)+sin^2 (B/2) + sin^2 (C/2) = 1-2sinA.sinB.sinC# ?

2 Answers
Apr 29, 2018

Fun. Let's check it before we spend too much time on it.

For the easiest numbers, let #A=90^circ, B=C=0^circ.# We get #sin^2 45^circ = 1/2# on the left and # 1 - 2 \ sin 90^circ sin 0 sin 0 = 1# on the right. It's false. Cue the deflated trombone, wah wah waaah.

Apr 29, 2018

question is incorrect.