Trigonometry Help
posted by Anonymous on .
Simplify:
sin(xy)cosy+cos(xy)siny
= (sinxcosycosxsiny)cosy+(cosxcosy+sinxsiny)siny
= ???
What do I do next???
Please Help and Thank You

expand it again
= sinx cos^2 y  cosxsinycosy + cosxcosysiny + sinxsin^2 y
= sinx(cos^2 y  sin^2 y)
= sinxcos(2y) 
when I substitue the x's and y's I get different answers.
do I need brackets on (sinxcosycosxsiny) and (cosxcosy+sinxsiny)?
could the next step be: sinxcosycosxsinycosy+cosxcosy+sinxsinysiny without the brackets? or would that be wrong? 
found my error
2nd last line should have been
= sinx(cos^2 y + sin^2 y)
= sinx (1)
= sinx 
thank you so much=)