Would anybody happen to know how to express this in terms of X?
Saying is the same as saying . Since tangent is "opposite side over near side", if we imagine a right triangle with legs of length 7 and x, is the angle opposite the leg of length 7. Now we can use the Pythagorean theorem to find the length, c, of the hypotenuse: so .
Now secant is 1/sine or "hypotenuse divided by opposite side" which, here, is . Finally, .