document.write( "Question 1092900: If tan x=20/21, and, pi < x < 3pi/2 what is sin (x+pi/2)
\n" ); document.write( "Enter your answer as a fraction in simplest form, like this: 3/14 \n" ); document.write( "

Algebra.Com's Answer #707517 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Note that $\"+x+\"$ is in the 3rd quadrant, so actually
\n" ); document.write( " $\"+tan%28x%29+=+%28-20%29%2F%28-21%29+\"$
\n" ); document.write( " $\"+%28-20%29%2F%28-21%29+=+20%2F21+\"$
\n" ); document.write( "-----------------------------------
\n" ); document.write( "The length of the rotating vector is:
\n" ); document.write( " $\"+c+=+sqrt%28+20%5E2+%2B+21%5E2+%29+\"$
\n" ); document.write( " $\"+c+=+sqrt%28+400+%2B+441+%29+\"$
\n" ); document.write( " $\"+c+=+sqrt%28+841+%29+\"$
\n" ); document.write( " $\"+c+=+29+\"$
\n" ); document.write( "---------------
\n" ); document.write( "Since a general rule is: $\"+sin%28+x+%2B+pi%2F2+%29+=+cos%28+x+%29+\"$
\n" ); document.write( " $\"+cos%28+x+%29+=+-21%2F29+\"$
\n" ); document.write( "-----------------------
\n" ); document.write( "Note that if $\"+pi+%3C+x+%3C+3pi%2F2+\"$ , then
\n" ); document.write( " $\"+x+%2B+pi%2F2+\"$ is an angle in the 4th quadrant
\n" ); document.write( "where the sin function is negative
\n" ); document.write( " \n" ); document.write( "

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