For the point #(-4,-6)# we can create a right triangle with legs of #x = -4# and #y =-6#
Using the pythagorean theorem we get the hypotenuse.
#a^2 + b^2 = c^2#
#(-4)^2 + (-6)^2 = hyp^2#
#16+36=hyp^2#
#52 = hyp^2#
#sqrt52 = hyp#
#2sqrt13 = hyp#
The six trig functions are
#sintheta = (opp)/(hyp)#
#costheta = (adj)/(hyp)#
#tantheta = (opp)/(adj)#
#sectheta = (hyp)/(adj)#
#csctheta = (hyp)/(opp)#
#ctntheta = (adj)/(opp)#
#sintheta = (-6)/(2sqrt13) = -3/sqrt13 * sqrt13/sqrt13 = -3sqrt13/13#
#costheta = (-4)/(2sqrt13) = -2/sqrt13 * sqrt13/sqrt13 = -2sqrt13/13#
#tantheta = (-6)/-4 = 3/2#
#sectheta = (2sqrt13)/-4 = -sqrt13/2#
#csctheta = (2sqrt13)/-6 = -sqrt13/3#
#ctntheta = (-4)/-6 = 2/3#