Question
Mathematics Question on Matrices
The domain of f(x)=cos−1(7x) is:
A
[−71,71]
B
[−7,7]
C
[0,7]
D
[−1,1]
Answer
[−71,71]
Explanation
Solution
The function cos−1(x) is defined only for x∈[−1,1]. Here, f(x)=cos−1(7x), so 7x must also lie in the interval [−1,1]. Solve the inequality:
−1≤7x≤1.
Divide through by 7:
−71≤x≤71.
Thus, the domain of f(x)=cos−1(7x) is [−71,71].