Explanation:
cos60° = Adjacent/Hypotenuse = a/42.
=> a = 42cos60° = 21.
sin60° = Opposite/Hypotenuse d/42.
=> d = 42sin60° = 42(√3/2) = 21√3.
tan30° = Opposite/Adjacent = d/b.
=> b = d / tan30° = (21√3) / (1/√3) = 63.
sin30° = Opposite/Hypotenuse = d/c.
=> c = d / sin30° = (21√3) / (1/2) = 42√3.