Question

помогите

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Answer 1

1) AB^2=16+3*16=4*16

    AB=8

   cosB=4/8=1/2

2) cosA=AC/AB

   AC^2=64-15*4=4

  AC=2

cosA=2/8=1/4

3)cosA=AC/AB=16/sqrt(16^2+144)=16/20=0,8