Jika cos (A+B) = 100/125 dan cos (A-B) = - 44/125, maka nilai dari tanAtanB =. . . . . .

cos (a + b) = 100/125
cos a cos b - sin a sin b = 100/125

cos (a - b) = -44/125
cos a cos b + sin a sin b = -44/125

cos a cos b - sin a sin b = 100/125
cos a cos b + sin a sin b = -44/125
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2 cos a cos b = 56/125
cos a cos b = 28/125

cos a cos b + sin a sin b = 44/125
28/125 + sin a sin b = 44/125
sin a sin b = 44/125 - 28/125
sin a sin b= 16/125

tan a tan b = ?
=  sin a sin b 
   cos a cos b
= 16/125 : 28/125
=  16  x 125
   125     28
= 16/28
= 4/7