diketahui (A+B) = π/3 dan sin A sin B =1/4 ditanyak cos (A-B) adalah...

[tex]a + b = \frac{\pi}{3} [/tex]
a + b = 60°
[tex] \cos(a + b) = \cos(60) = \frac{1}{2} [/tex]
[tex] \sin(a) \sin(b) = \frac{1}{4} [/tex]
[tex] \cos(a + b) = \cos(a) \cos(b) - \sin(a) \sin(b) \\ \frac{1}{2} = \cos(a) \cos(b) - \frac{1}{4} \\ \frac{1}{2} + \frac{1}{4} = \cos(a) \cos(b) \\ \cos(a) \cos(b) = \frac{2}{4} + \frac{1}{4 } \\ \cos(a) \cos(b) = \frac{3}{4} [/tex]
[tex] \cos(a - b) = \cos(a) \cos(b) + \sin(a) \sin(b) \\ \cos(a - b) = \frac{3}{4} + \frac{1}{4} \\ \cos(a - b) = 1[/tex]
Semoga dapat dipahami