Tolong jawab dong plisss

sin a = 4/5 maka cos a = 3/5
sin b = 5 /13 maka cos b =12/13
cos (a-b)= cos a cos b + sin a sin b
= 3/5 . 12/13 + 4/5 . 5/13
=36/65 + 20/65
=56/65
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