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 #782281 by math_helper(2461) $\"\"$ $\"About$

You can put this solution on YOUR website!


\n" );
document.write( "I assume a is  and b is ...\r
\n" );
document.write( "\n" );
document.write( "The trig functions take ANGLES as inputs, you can not plug in the output of other trig functions as those are RATIOS.   As such, you need to find angles a and b first:\r
\n" );
document.write( "\n" );
document.write( "a =   (made use of \"angle in Q2\")
\n" );
document.write( "b =   (made use of \"angle in Q3\")\r
\n" );
document.write( "\n" );
document.write( "Now you can plug a and b into the equations:\r
\n" );
document.write( "\n" );
document.write( "1.  sin(a+b) = sin(126.870 + 208.072) = sin(334.942) = -0.424\r
\n" );
document.write( "\n" );
document.write( "etc.\r
\n" );
document.write( "\n" );
document.write( " \n" );
document.write( "

\n" );