document.write( "Question 1031684: Write the equation –2x + 6y = 9 in polar form.\r
\n" ); document.write( "\n" ); document.write( "7√(10)/20 = r cos(Ө – 72°)
\n" ); document.write( "9√(10)/20 = r cos(Ө – 72°)
\n" ); document.write( "9√(10)/20 = r cos(Ө – 108°)
\n" ); document.write( "7√(10)/20 = r cos(Ө – 108°) \n" ); document.write( "
Algebra.Com's Answer #646404 by Edwin McCravy(20056)\"\" \"About 
You can put this solution on YOUR website!
\r\n" );
document.write( "The choices involve either 72° or 108°, neither of which\r\n" );
document.write( "are special angles, so to get those answers is going to\r\n" );
document.write( "take some high powered trigonometry.  So the easiest way \r\n" );
document.write( "to get the correct answer it to take an arbitrary \r\n" );
document.write( "point on the line –2x + 6y = 9, convert it to polar form,\r\n" );
document.write( "substitute it in the four answers and see which one, if\r\n" );
document.write( "any, it checks in.\r\n" );
document.write( "\r\n" );
document.write( "–2x + 6y = 9\r\n" );
document.write( "\r\n" );
document.write( "If x = -4.5, y=0, that's the x-intercept.\r\n" );
document.write( "\r\n" );
document.write( "So (-4.5,0) is a rectangular point on the given line.\r\n" );
document.write( "\r\n" );
document.write( "The rectangular point (-4.5,0) \r\n" );
document.write( "is the same as the polar point\r\n" );
document.write( "\r\n" );
document.write( "(r,Ө) = (4.5,180°)  \r\n" );
document.write( "\r\n" );
document.write( "The choices are:\r\n" );
document.write( "\r\n" );
document.write( "7√(10)/20 = r cos(Ө – 72°)\r\n" );
document.write( "9√(10)/20 = r cos(Ө – 72°)\r\n" );
document.write( "9√(10)/20 = r cos(Ө – 108°)\r\n" );
document.write( "7√(10)/20 = r cos(Ө – 108°)\r\n" );
document.write( "\r\n" );
document.write( "The left sides of the first and last choices\r\n" );
document.write( "are the same 7√(10)/20 = 1.106797181\r\n" );
document.write( "\r\n" );
document.write( "The left sides of the second and third choices\r\n" );
document.write( "are the same 9√(10)/20 = 1.423024947\r\n" );
document.write( "\r\n" );
document.write( "If we substitute r=4.5 and Ө=180°, the right\r\n" );
document.write( "side of the first two choices \r\n" );
document.write( "gives -1.390576475\r\n" );
document.write( "\r\n" );
document.write( "If we substitute the same in the right side of the\r\n" );
document.write( "last two choices we get 1.390576475.\r\n" );
document.write( "\r\n" );
document.write( "So none of those answers can possibly be correct!!!\r\n" );
document.write( "\r\n" );
document.write( "Edwin
\n" ); document.write( "
\n" );