document.write( "Question 1058785: Can you help me solve this expression in order to find out where it is true?\r
\n" ); document.write( "\n" ); document.write( " $\"+cos%28-7pi%2F2%29+\"$ = $\"+cos%28pi+%2B+pi%2F2%29+\"$ \n" ); document.write( "

Algebra.Com's Answer #673883 by Boreal(15235) $\"\"$ $\"About$

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cos (-7pi/2)=cos(-pi/2)=0, because one can add 2pi multiples without changing the location to get -5pi/2, -3pi/2, and -pi/2
\n" ); document.write( "Therefore, cos (pi+pi/2)=0. That is cos (3 pi/2), where it occurs. 270 degrees. ANSWER
\n" ); document.write( "It is also cos (pi)*cos(pi/2)-sin (pi)*sin (pi/2)=0
\n" ); document.write( "The first is -1*0-0(1)=0, so it is an identity.
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