Trigonometry Help
posted by Anonymous .
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=)
Respond to this Question
Similar Questions

calc
what is the derivative of sinx cosy = 0 in its simplest form? 
Math help again
cos(3π/4+x) + sin (3π/4 x) = 0 = cos(3π/4)cosx + sin(3π/4)sinx + sin(3π/4)cosx  cos(3π/4)sinx = 1/sqrt2cosx + 1/sqrt2sinx + 1/sqrt2cosx  (1/sqrt2sinx) I canceled out 1/sqrt2cosx and 1/sqrt2cosx Now … 
Trig (inverse functions)
Problem: tan[arccsc(5/3) + arctan(1/4)] My work: let arccsc(5/3)=X and let arctan(1/4)=Y where pi/2<=X<=pi/2, X cannot be 0 and where pi/2<Y<pi/2 so that cscX=5/3 and tanY=1/4 The problem can now be written as tan(X+Y) … 
Trigonometry
Prove that (cosy/1+siny) + (1+siny/cosy) = 2secy 
trig
Okay, I've been getting some of these, but I can't seem to verify this identity... any help? 
Trigo help!
Ok, i've tried this question, and it brings me to no answers. Please help! Prove the following: secY(1+tanY)=6cosecY my workings: LeftHandSide: secY + tanY/cosY = 1/cosY + sinY/cos^2Y =(cosY+sinY)/cos^2Y = ? 
maths (trigonometry)
please solve these if possible Q1. If sinx +siny=3(cosycosx) then the value of sin3x/sin3y. Q2. If sina ,cosa,and tan a are in g.p.then cos cubea+cos square a is equal to 
Math
Suppose f(x) = sin(pi*cosx) On any interval where the inverse function y = f –1(x) exists, the derivative of f –1(x) with respect to x is: a)1/(cos(pi*cosx)), where x and y are related by the equation (satisfy the equation) x=sin(pi*cosy) … 
Math
How do I get (sinx cosy + cosx siny) (cosx cosy + sinx siny) in the form of 1/2(sin2x + sin2y)? 
calculus help
y=cosxcosysinxsiny/sinxcosy+cosxsiny find dy/dx plz show me working