sin A = 1/5 dengan A dikuadran II. maka tentukan nilai sin A/2 ?

Kuadran 2 (sin + , cos -)
sin A = 1/5
cos A = √(1 - sin² A)
cos A = √((25 - 1)/25)
cos A = -1/5 √24
cos A = -2/5 √6

cos A = cos 2(1/2 A)
cos 2(1/2 A) = 1 - 2sin² (1/2 A)
2 sin² (1/2 A) = 1 + 2/5 √6
sin² (1/2 A) = 1/2 (1 + 2/5 √6)
sin² (1/2 A) = 1/10 (5 + 2√6)
sin² (1/2 A) = 1/100 (50 + 20√6
sin (1/2 A) = √(1/100 (50 + 20√6))
sin (1/2 A) = (1/10)√(50 + 2√600)
sin (1/2 A) = (1/10)(√30 + √20)
sin (1/2 A) = (1/10)(√30 + 2√5)