Question 918469
Refer to a graph of the unit circle with labeled reference angles.


t is just a little bit greater than {{{pi}}}.  The sine will also be negative if the terminal point is in quadrant III.


Use either a scientific calculator or a table of trigonometric function values to find the "arc whose cosine is " {{{-12/13}}}; you will use the decimal value for this cosine.


You could use the Pythagorean relationship between sine and cosine to find sine of t:
{{{sin^2(t)+cos^2(t)=1}}}