Cos(22/7/4-x) cos22/7/4-y) - sin(22/7/4-x)sin(22/7/4-y) =sin(x+y)

1.	Cos(22/7/4-x) cos22/7/4-y) - sin(22/7/4-x)sin(22/7/4-y) =sin(x+y)
Answer» We have L.H.S=. {tex}\\cos \\left( {\\frac{\\pi }{4} - x} \\right)\\cos \\left( {\\frac{\\pi }{4} - y} \\right)\\sin \\left( {\\frac{\\pi }{4} - x} \\right){/tex}{tex}\\sin \\left( {\\frac{x}{4} - y} \\right){/tex}{tex} = \\cos \\left[ {\\frac{\\pi }{4} - x + \\frac{\\pi }{4} - y} \\right]{/tex}[ {tex}\\because {/tex}cos (A+ B) = cos A cos B - sin A sin B]{tex} = \\cos \\left[ {\\frac{\\pi }{2} - (x + y)} \\right]{/tex}= sin (x + y) = R.H.S

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