Question 212759
If sin(theta) =12/13 in the second quadrant, then the reference triangle has "opposite side" of 12 and hypotenuse 13.  This means that the "adjacent side" is 5, and since it is in the second quadrant, it is -5.  


Sec(theta) is {{{(hyp)/(adj) }}}={{{13/-5}}}.


R^2


Retired from trig for about 15 years!!!