Question

Dik tan a=3/4 dan tan b=5/6 a dan b sudut lancip maka nilai cos (a+b)?

Answer 1

Tan a= 3/4
sin a = 3/5
cos a = 4/5

tan b = 5/6
sin b = 5/V61
cos b = 6/V61

cos (a+b) = cos a.cosb - sin a. sin b
= 4/5 . 6/V61 - 3/5 . 5/V61
= 24/5V61 - 3/V61
= 9/5V61