NDA 2016
- Exam
- NDA
- Year
- 2016
- Subject
- Mathematics
- Chapter
- Inverse Trigonometric Functions
NDA 2016 · Mathematics · Inverse Trigonometric Functions
What is the value of (2 ^ -1 (0.8). ?
What is the value of ?
Options
- A
- B
- C
- D
Correct answer
D.
Step-by-step solution
We know that
\begin{aligned}
& 2 \cos ^{-1} x=\cos ^{-1} x\left(2 x^2-1\right) \\
& \text{ here } x=0.8 \\
& \begin{aligned}
\therefore \quad 2 \cos ^{-1}(0.8) & =\cos ^{-1}\left(2(0.8)^2-1\right) \\
& =\cos ^{-1}(0.28)
\end{aligned}
\end{aligned}\left(\cos ^{-1}(x)\right)=x$.
\therefore \cos \left(\cos ^{-1}(0.28)\right)=0.28