document.write( "Question 1149958: how do i verify the identity of sin(x+pi/2)=cos x
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Algebra.Com's Answer #771288 by ikleyn(52780)\"\" \"About 
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document.write( "Apply the addition formula for sine\r\n" );
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document.write( "    sin(a+b) - sin(a)*cos(b) + cos(a)*sin(b).     (1)\r\n" );
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document.write( "It is one of the basic formula of Trigonometry; it is valid for all angles  \"a\" and  \"b\".\r\n" );
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document.write( "Put  a = x  and  b = \"pi%2F2\".  You will get\r\n" );
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document.write( "    \"sin%28x+%2B+pi%2F2%29\" = \"sin%28x%29%2Acos%28pi%2F2%29\" + \"cos%28x%29%2Asin%28pi%2F2%29\".    (2)\r\n" );
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document.write( "Take into account that   \"cos%28pi%2F2%29\" = 0,   \"sin%28pi%2F2%29\" = 1.\r\n" );
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document.write( "Then you can continue the line (2) in this way\r\n" );
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document.write( "         \"sin%28x+%2B+pi%2F2%29\" = \"sin%28x%29%2Acos%28pi%2F2%29\" + \"cos%28x%29%2Asin%28pi%2F2%29\" = sin(x)*0 + cos(x)*1 = cos(x).\r\n" );
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document.write( "Thus the identity  \"sin%28x%2Bpi%2F2%29\" = =cos x  is proved for all angles  x.\r\n" );
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