Diketahui sin A = √5/3 , 0 < A < 1/2 π Maka: A). Tentukan nilai dari cos 1/2 A​

trigonometri

interval 0 < A < 1/2 π Kuadran I

nilai sin cos tan (+)

sin A = √5 /3

sin² A + cos² A = 1

cos A

= √(1 – sin² A)

= √(1 – (√5 / 3)²)

= √(1 – 5/9)

= √((9 – 5)/9)

= √(4/9)

= 2/3

•

cos A = 2 cos² (1/2 A) – 1

cos² (1/2 A)

= (cos A + 1)/2

= (2/3 + 1)/2

= (5/3)/2

= 5/6

cos (1/2 A)

= √(5/6)

= √5/√6

= 1/6 √30