document.write( "Question 1207479: If z1 , z2 are two complex numbers , |z1|=|z2| , and Arg(z1 + z2) = pi/4 ,find Arg(z1×z2) \n" ); document.write( "
Algebra.Com's Answer #845373 by ikleyn(52799)\"\" \"About 
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document.write( "arg(z1*z2) is always equal to arg(z1) + arg(z2)    (by the modulo of \"2pi\").\r\n" );
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document.write( "From the other side, if  |z1| = |z2|,  then arg(z1+z2) = \"%28arg%28z1%29%2Barg%282%29%29%2F2\" \r\n" );
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document.write( "according to the parallelogram rule of adding vectors (= complex numbers), which\r\n" );
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document.write( "is in this case the \"rhombus\" rule of adding vectors.\r\n" );
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document.write( "From this, we conclude that, under given conditions,\r\n" );
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document.write( "    arg(z1*z2) = arg(z1) + arg(z2) = \"2%2A%28%28arg%28z1%29+%2B+arg%28z2%29%29%2F2%29\" = 2*arg(z1+z2) = \"2%2A%28pi%2F4%29\" = \"pi%2F2\".    ANSWER\r\n" );
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