We know that:
#tantheta=sintheta/costheta#
and
#cottheta=1/tantheta#
So we can plug in our values:
#color(white)=cot(theta)#
#=1/tan(theta)#
#=1/(sintheta/costheta)#
#=1/(sintheta/costheta)color(blue)(*costheta/costheta)#
#=1/(sintheta/color(red)cancelcolor(black)costheta)color(blue)(*costheta/color(red)cancelcolor(blue)costheta)#
#=1/sinthetacolor(blue)(*costheta)#
#=costheta/sintheta#
Now plug in our values:
#=(-12/13)/(-5/13)#
#=(-12/13)/(-5/13)color(blue)(*13/13)#
#=(-12/color(red)cancelcolor(black)13)/(-5/color(red)cancelcolor(black)13)color(blue)(*color(red)cancelcolor(blue)13/color(red)cancelcolor(blue)13)#
#=(-12)/(-5)color(blue)(*1/1)#
#=(-12)/(-5)#
#=(color(red)cancelcolor(black)-12)/(color(red)cancelcolor(black)-5)#
#=12/5#
That's the solution. Hope this helped!