Question

Jngan cuma liat poinnya ya,, !!
NILAI segitiga ABC diketahui AB=8 cm,BC=11 cm dan CA=5 cm.jika alfa sudut dihadapan sisi BC,maka 10 sin alfha =.....
(pake cara!)

Answer 1

BC² = AB² + AC² - 2.AB.AC Cosα
(11)² = (8)² + (5)² - 2.8.5 Cosα
121 = 64 + 25 - 80 Cosα
121 = 89 - 80 Cosα
- 80 Cosα = 32
Cosα = - 32/80
Cosα = -2/5

sin²α = 1 - cos²α
(=) 1 - (-2/5)²
(=) 1 - (4/25)
(=) 25 - 4 / 25
(=) 21 / 25
sinα = √21/25
(=) √21 / 5
(=) 1/5√21

sin 10α = (10)(1/5√21)
(=) 10/5√21
(=) 2√21