Question 826533
{{{pi/2 = (1/2)pi}}}
{{{3pi/4 = (3/4)pi}}}
{{{pi = 1*pi}}}
Looking at {{{3pi/4}}} as three fourths {{{pi}}} helps us figure out that it is greater than {{{pi/2}}} but less than {{{pi}}}. So {{{3pi/4}}} terminates in the second quadrant.<br>
sin is positive in the second quadrant so it cannot be {{{-sqrt(2)/2}}}.