Question

Jika Sin α = 5/13 dengan 90° ≤ α ≤ 180° maka nilai dari sin 2a adalah...

Answer 1

Verified answer

Sin²a+cos²a=1
cos²a=1-sin²a
cos²a=1-(5/13)²
cos²a=1-25/169
cos²a=169-25/169
cos²a=144/169 
cosa= 12/13 kuadran 2 = -12/13
sin2a= 2sinacosa
sin2a=2(5/13)(-12/13) = -120/169 

Answer 2

Verified answer

Jawab
α di kuadran II , tumpul
sin α  = 5/13 = y/r
y= 5, r = 13, x = 12
cos α  = - x/r = - 12/13
sin 2α  = 2 sin α cos α
sin 2α  = 2(5/13)(- 12/13) = - 120/169