the question asks to integrate cos(t)/ (5sin(t)+8)^2 the answer i got was xcos(t)/(5sin(t)+8)^2 this is not right i believe there is something wrong with the x in front of the cos.... please heplp

Use the substitution

u=sin(t)
du=cos(t)dt
and don't forget the factor (1/5) when you do the second substitution
v=(5u+8)