Sin 5 derajat + sin 175 derajat =

sin α + sin β = 2 sin 1/2 (α+β) cos 1/2 (α-β)
= 2 sin 1/2 (5°+175°) cos 1/2 (5°-175°)
= 2 sin 1/2 (180°) cos 1/2 (170°)
= 2 sin 90° · cos 135°
= 2.1/2√2.-1/2√2
= -1/2√4