Create a diagram with angle x in standard position with its terminal ray in QIV intersecting a circle w radius 7 centered on the origin. Draw a perpendicular back to the x-axis from that point of intersection to form a right triangle whose hypotenuse (the circle's radius) is labeled as 7. The y-coordinate of that point of intersection, which is also the "length" of the leg opposite x's reference angle, is = - 4. Use pythagorean theorem to calculate the x-coordinate (the adjacent leg), which will be √35.
Thus, cosx = √35 / 7 and secx = 7 / √35 = 7√35 / 35 = √35 / 5
