Bantuin dongg makasii mat ini trigonometri yaa makasi

cos (A + B) = 1/2
cos A cos B - sin A sin B = 1/2
cos A cos B - 1/5 = 1/2
cos A cos B = 1/2 + 1/5
cos A cos B = 7/10

Tan A Tan B = sin A sin B / cos A cos B
= (1/5)/(7/10) =2/7