cos(arcsin 5/13 + П/2)/sin(arcsin 5/13 + П/2) =
= [cos(arcsin 5/13)*cos(П/2) - sin(arcsin 5/13)*sin(П/2)]/[sin(arcsin 5/13)*cos(П/2) + + cos(arcsin 5/13)*sin(П/2)] = [cos(arcsin 5/13)*0 - 5/13*1]/[5/13*0 + + cos(arcsin 5/13)*1] = (-5/13)/cos(arcsin 5/13) = -(5/13)/[1 - sin^2(arcsin 5/13)]^0.5 = -(5/13)/[1 - (5/13)^2]^0.5 = -(5/13)/[1 - 25/169]^0.5 =
= -(5/13)/(144/169)^0.5 = -(5/13)/(12/13) = -5/12