sin(-1290°)
Using a trig identity, we have
sin(-1290°) = - sin(1290°)
First, express 1290/360 as a mixed number = 3 + 7/12
Disregard the "whole" part and multiply the fraction by 360
This gives 210...and sin(210) = - (1/2)
But, we need the negative of this .... = 1/2
Of course.....putting the original thing into the on-site calculator would be faster ..... !!!!