Algebra.Com's Answer #821592 by ikleyn(52797)![\"\"](\"/images/stars/stars-13.gif\")  
You can put this solution on YOUR website!
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document.write( "Please help me with this question, If SinA=2/3,and A is obtuse, find the exact value of,
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document.write( "1)cosA, 2)sin2A, 3) tan2A
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document.write( " The solution by @MathLover1 is INCORRECT.\r
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document.write( " I came to bring a correct solution.\r
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document.write( "(1) cos(A) =  =  =  =  =  .\r\n" );
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document.write( " Since A is obtuse, angle A is in QII, where cosine is negative, so we use sign \" - \" at the square root.\r\n" );
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document.write( " It is first difference from the solution by @MathLover1.\r\n" );
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document.write( "(2) sin(2A) = 2*sin(A)*cos(A) =  =  .\r\n" );
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document.write( " Notice sign \" - \" in my answer. It is the second difference from the solution by @MathLover1.\r\n" );
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document.write( "(3) tan(2A) =  =  =  =  =  =  .\r\n" );
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document.write( " Notice sign \" - \" in my answer. It is the third difference from the solution by @MathLover1.\r\n" );
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document.write( "Solved (correctly).\r
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