document.write( "Question 1074693: The line with equation y + 2x = 0 coincides with the terminal side of an angle θ in standard position in Quadrant IV .\r
\n" ); document.write( "\n" ); document.write( "What is the value of tan0?\r
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\n" ); document.write( "\n" ); document.write( "The line with equation −a+3b=0 coincides with the terminal side of an angle θ in standard position and sin θ<0 .\r
\n" ); document.write( "\n" ); document.write( "What is the value of cosθ ?\r
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Algebra.Com's Answer #689387 by KMST(5328)\"\" \"About 
You can put this solution on YOUR website!
1) Line \"y%2B2x=0\"
\n" ); document.write( " Maybe your teacher instructor defined trigonometric functions
\n" ); document.write( "based on the coordinates of \"P%28x%5BP%5D%2Cy%5BP%5D%29\" , with .
\n" ); document.write( "My 9th grade math teacher defined \"than%28theta%29=y%5BQ%5D\" .
\n" ); document.write( "Either way it is \"tan%28theta%29=y%5BR%5D%2Fx%5BR%5D\" for some point \"R%28x%5BR%5D%2Cy%5BR%5D%29\"
\n" ); document.write( "on that blue line that passes through the origin \"O%280%2C0%29\" ,
\n" ); document.write( "\"y%2B2x=0\" <---> \"y=-2x\" .
\n" ); document.write( "Of course that \"tan%28theta%29=y%5BR%5D%2Fx%5BR%5D=%28y%5BR%5D-0%29%2F%28x%5BR%5D-0%29\" is the slope of the line,
\n" ); document.write( "and the slope of \"y=-2x\" is \"highlight%28-2%29%29\" ,
\n" ); document.write( "the coefficient of \"x\"
\n" ); document.write( "in the slope-intercept form of the equation of the line.
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\n" ); document.write( "1) Line \"-a%2B3b=0\"
\n" ); document.write( "would have to be graphed on a pait if a-b axes.
\n" ); document.write( "I would use the usual x-y axes and say that \"system+%28a=x%2Cb=y%29\" .
\n" ); document.write( "Then, the line would be \"-x%2B3y=0\" <--> \"3y=x\" <--> \"y=%281%2F3%29x\" .
\n" ); document.write( "\"tan%28theta%29=1%2F3\"
\n" ); document.write( "If \"sin%28theta%29%3E0\" ,
\n" ); document.write( "\"sin%28theta%29=sqrt%281-cos%5E2%28theta%29%29\" and
\n" ); document.write( "since \"tan%28theta%29=sin%28theta%29%2Fcos%28theta%29\" ,
\n" ); document.write( "\"sqrt%281-cos%5E2%28theta%29%29%2Fcos%28theta%29=1%2F3\"
\n" ); document.write( "\"sqrt%281-cos%5E2%28theta%29%29=cos%28theta%29%2F3\"
\n" ); document.write( "Squaring both sides,
\n" ); document.write( "\"1-cos%5E2%28theta%29=cos%5E2%28theta%29%2F9\"
\n" ); document.write( "\"9-9cos%5E2%28theta%29=cos%5E2%28theta%29\"
\n" ); document.write( "\"9=10cos%5E2%28theta%29\"
\n" ); document.write( "\"9%2F10=cos%5E2%28theta%29\"
\n" ); document.write( "\"sin%28theta%29=sqrt%281-9%2F10%29\"
\n" ); document.write( "\"sin%28theta%29=sqrt%281%2F10%29\"
\n" ); document.write( "and
\n" ); document.write( "\"highlight%28sin%28theta%29=sqrt%2810%29%2F10%29\"
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