document.write( "Question 756722: If x is in the first and y is in the second quadrant, sin = 24/25, and sin y = 4/5, find the exact value of sin (x+y), cos(x-y). tan (x-y). I have sin(x+y) = (sinx)(cosy) + (cosx)(siny) = (24/25)(cosy) + (cosx)(4/5). Am I going about this the correct way? Then I figured (not sure if correct) cos y = -3/5 and cos x = 7/25. Putting that all into the equation I get (-72/125)+ (28/125) = Sin (x+y)\r
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Algebra.Com's Answer #460413 by Edwin McCravy(20056)\"\" \"About 
You can put this solution on YOUR website!
x is in the first and y is in the second quadrant, sin = 24/25, and sin y = 4/5, find the exact value of sin (x+y), cos(x-y). tan (x-y). I have sin(x+y) = (sinx)(cosy) + (cosx)(siny) = (24/25)(cosy) + (cosx)(4/5). Am I going about this the correct way? Then I figured (not sure if correct) cos y = -3/5 and cos x = 7/25. Putting that all into the equation I get (-72/125)+ (28/125) = Sin (x+y) =
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document.write( "That is correct: sin(x+y) = (-72/125)+(28/125) = = -44/125  \r\n" );
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document.write( "However this expression is wrong:\r\n" );
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\n" ); document.write( "= Sin (24/25+ 4/5) =
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document.write( "The 24/25 and the 4/5 are sines, not angles, and writing the above is\r\n" );
document.write( "incorrect because that looks like \"the sine of the sum of two sines\",\r\n" );
document.write( "\"not the sum of two angles\".\r\n" );
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document.write( "Correct final answers:  \r\n" );
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document.write( "sin(x+y) = -44/125\r\n" );
document.write( "cos(x-y) = 3/5\r\n" );
document.write( "tan(x-y) = -4/3\r\n" );
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document.write( "Edwin
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