Answer: x = 41.4°
Explanation:
We want to solve:
Cos(x) = 3/4
Such that this is on quadrant 1.
(if x is in degrees, the possible values of x will be: 0° ≤ x ≤ 90°)
To solve this we need to remember the inverse functions.
If we have two functions f(x) and g(x), these functions are inverses if:
f( g(x) ) = x
g( f(x) ) = x
Then the inverse of the cosine function (this function is "arcos(x)") is such that:
Arcos( cos(x) ) = x
Then in our equation:
Cos(x) = 3/4
We can apply the inverse function to both sides to get:
Arcos(Cos(x)) = Arcos(3/4)
x = Arcos(3/4)
(To find the Arcos function in your calculator, you need to use the button "inv" and then the "cos" button, and remember to have your calculator in deg mode)
x = Arcos(3/4) = 41.4°