Trig Function Question. HELP! (1 Viewer)

[cyndix3]

Hi,

Hope you guys can help me! Im having difficulties integrating this trig function: sin3xcos2x




Thanx heaps in advanced!

 

[Bored Of Fail 2]

use so called product to sum formula

sin(A+B ) + sin(A-B) = sinAcosB + cosAsinB + sinAcosB -cosAsinB = 2 sinAcosB

therefore sinAcosB = (1/2) ( sin(A+B) + sin(A-B) )

so set A=3x , B=2x

we want the integral (1/2) ( sin(5x) + sin(x) )

we want (1/2) integral ( sin(5x) -sin(x) ) dx = (1/2) ( (-1/5) cos(5x) -cos(x) ) +C

 

[Bored Of Fail 2]

The product to sum formulas can be derived relatively easily, and you can find them all on wikipedia, remember the derivations though, not the formula itself