The terminal ray of ∠A passes through the point (10,−4) . ∠A is drawn in standard position.

First find the hypotenuse

 

sqrt (10^2 +(-4)^2 = 10.77

 

cos = adj/hypotenuse

       = 10/10.77 = .92847          sec = 1/cos = 1/.92847 = 1.077