Question

Find exact value of sin2(20°) + sin2(70°).?

Don't use a calculator.

Answers

70 is 90 - 20, hence sin(70) = cos(20).

Hence sin^2(20) + sin^2(70) = sin^2(20) + cos^2(20) = 1

#1

sin 20 ° = cos 70 °

sin 2 20 ° + sin 2 70 ° = cos 2 70 ° + sin 2 70 ° = 1

#2

sin2(20°) + sin2(70°) = (0.342)2 + (0.9397)2

sin2(20°) + sin2(70°) = 0.117 + 0.883

sin2(20°) + sin2(70°) = 1. ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Answer

#3