document.write( "Question 1159221: If tan α = − 4/3 and cot β = 15/8
\n" ); document.write( " for a second-quadrant angle α and a third-quadrant angle β, find the following.
\n" ); document.write( "1. sin (a+b)
\n" ); document.write( "2. cos (a+b)
\n" ); document.write( "3. tan (a+b)\r
\n" ); document.write( "\n" ); document.write( "I got -5 for #1, 20 for #2, and 13/84 for #3. They are all wrong and I do not know why. Maybe because I just substituted the fractions I was given into the equations? \n" ); document.write( "

Algebra.Com's Answer #782292 by MathTherapy(10858) $\"\"$ $\"About$

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If tan α = − 4/3 and cot β = 15/8
\n" ); document.write( " for a second-quadrant angle α and a third-quadrant angle β, find the following.
\n" ); document.write( "1. sin (a+b)
\n" ); document.write( "2. cos (a+b)
\n" ); document.write( "3. tan (a+b)\r
\n" ); document.write( "\n" ); document.write( "I got -5 for #1, 20 for #2, and 13/84 for #3. They are all wrong and I do not know why. Maybe because I just substituted the fractions I was given into the equations?
\n" ); document.write( "

           
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document.write( "           As this is a 3-4-5 right-triangle, r = 5. This triangle exists in the 2nd quadrant 
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document.write( "Therefore,  \r
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document.write( "           
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document.write( "           As this is an 8-15-17 right-triangle, r = 17. This triangle exists in the 3rd quadrant, where cos and sin are < 0. 
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document.write( "Therefore, 
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document.write( " 
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document.write( "1.   
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document.write( "     
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document.write( "2.   
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document.write( "    
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document.write( "3.   
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document.write( "     \n" );
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