nilai cos M = .......

cos M = CM / KM
cos M = 4 / 2√13
           = 4√13 / 26
           = 2√13 / 13

jadi jawabannya B

cos M = samping/miring
= 4/2√13
= 2/√13

= 2√13 / (√13)(√13)
= 2/13 √13

B