Вычислить: ctg(arccos 4/5) cos(arctg(-5/12))

Question

Вычислить:

ctg(arccos 4/5)

cos(arctg(-5/12))

Answer 1

ctg(arccos 4/5) = 0,8/(√(1-0,8²)) = 0,8/0,6 = 4/3

cos(arctg (-5/12)) = 1/√(1+(-5/12)²) = 1/√(169/144)=1/(13/12)=12/13