Help please with a, b,c
also
in (a) in the answer sheet they've differentiated twice but I dont understand why?

(sin 42)/31. = sinx)/37

sinx = 37 (sin42)/31

= 37× 0.66/31 = 0.787

x= 51.9

other angle opposite to y = 180-51.9-42

= 180- 93.9 =86.1

so

sin42)/31 = sin 86.1)/y

0.021 = 0.997 /y

y= 0.997/0.021 =47.47

it is contrapositive

i could not see the question too well so check yourself again too . this is because i want you to get it correct.

x = 3 ± √(5+y)