Question

Integrating... (missing some kind of trig-related trick here)
\[\int 5\cdot sin(8x)\cdot cos(5x)\cdot dx \]

(medal for showing related substitutions :-) )

Answer 1

∫5⋅sin(8x)⋅cos(5x)⋅dx

Answer 2

a trig identity should solve your problem here\[\sin a\cdot\cos b=\frac12[\sin(a+b)+\sin(a-b)]\]

Answer 3

for future reference, I keep this file handy at all times
http://tutorial.math.lamar.edu/pdf/Trig_Cheat_Sheet.pdf

Answer 4

Ah... Ty @TuringTest :-)