I'm so stuck on this. I have no clue where to start.
sec (tan^-1 4)
(the tan is an inverse with the -1, 4 is the number)
Does this mean that you're not familiar with the meanings of the inverse trigonometric functions?
In case you're exaggerating a bit...
By definition, arctan(4) = A means tan(A) = 4 = 4/1.
Draw a right triangle. Label the non-right base angle as A. Label the "opposite" and "adjacent" sides as 4 and 1, respectively.
Use the Pythagorean Theorem to find the length of the hypotenuse.
Read the value of the sine from the triangle.
You are looking for the secant of the angle whose tangent is 4. Remember that in a right triangle, . Imagine a right triangle in which one leg (y) is four times as long as the other (x). This is indicated by the tangent (y/x) = 4. Hence,
Since the secant is r/x, it is equal to .