bantuin yah tolonggggggg

Jika alpa (¢) sudut dihadapan sisi a maka berlaku rumus
a^2 = b^2 + c^2 - 2bc cos ¢
7^2 = 3^2 + 5^2 - 2 . 3 . 5 cos ¢
49 = 9 + 25 - 30 cos ¢
30 cos ¢ = 9 + 25 - 49
30 cos ¢ = -15
cos ¢ = -1/2 => kuadran 2
cos ¢ = cos 120°

sin ¢ = sin 120° = 1/2 √3