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1 Marks Question

Question 511 Mark
Write the range of $\tan^{-1}\text{x}.$
Answer
The range of $\tan^{-1}\text{x}$ is $\Big(-\frac{\pi}{2},\frac{\pi}{2}\Big).$
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Question 521 Mark
Find the principal value of the following:
$\sin^{-1}\Big(\tan\frac{5\pi}{4}\Big)$
Answer
$\sin^{-1}\Big(\tan\frac{5\pi}{4}\Big)=\sin^{-1}(1)$
$\sin^{-1}\Big[\sin\Big(\frac{\pi}{2}\Big)\Big]=\frac{\pi}{2}$
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Question 531 Mark
Calculate the value of $ \sin−1\cos(\sin−1\text{x})+\cos−1\sin(\cos−1\text{x})$. where ∣x∣ ≤ 1.
  1. $ +\frac{\pi}{4}$
  2. $ -\frac{\pi}{4}$
  3. $ +\frac{\pi}{2}$
  4. $ -\frac{\pi}{2}$
Answer
  1. $ +\frac{\pi}{2}$
Solution:
Given, $ \displaystyle \sin^{-1} \cos \left ( \sin^{-1} \text{x}\right ) + \cos^{-1} \sin \left ( \cos^{-1} \text{x} \right )$
$ =\displaystyle \sin^{-1} \cos \left ( \cos^{-1} \sqrt{1-\text{x}^2}\right ) + \cos^{-1} \sin \left ( \sin^{-1} \sqrt{1-\text{x}^2} \right ) $
$ =\displaystyle \sin^{-1} \left(\sqrt{1-\text{x}^2}\right ) + \cos^{-1}\left ( \sqrt{1-\text{x}^2} \right ) =\frac{\pi}{2}$
Since $ \sin^{-1}\text{x}+\cos^{-1}\text{x} = \frac{\pi}{2} \forall |\text{x}|\leq $
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Question 541 Mark
If α and β are two real values of x which satisfy the equation  $\sin^{-1} \text{x} + \sin^{-1} (1−\text{x})=\cos^{−1}\text{x}, $then:
  1. $ \alpha + \beta = \frac{1}{2}$
  2. $ \alpha - \beta = \frac{1}{2}$
  3. $ \alpha - \beta = 0$
  4. $ \alpha - \beta = 6$
Answer
  1. $ \alpha + \beta = \frac{1}{2}$
Solution:
$ \sin^{-1}(\text{x})+\sin^{-1}(1-\text{x})=\cos^{-1}(\text{x})$
Now, x ϵ [-1, 1]
and -1 ≤ (1 - x) ≤ 1
x ϵ [0, 2]
Hence, x ϵ [0, 1]
Now we get two solutions of the above equation as 0 and $ \frac{1}{2}$
Thus, the two roots are
x = 0 and $ \text{x}=\frac{1}{2}$
$ α+β=\frac{2}{1}$
and $ \alpha\beta = 0$
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Question 551 Mark
$\cos^{-1}\bigg(\cos\frac{7\pi}{6}\bigg)$ is equal to:
  1. $\frac{7\pi}{6}$
  2. $\frac{5\pi}{6}$
  3. $\frac{\pi}{3}$
  4. $\frac{\pi}{6}$
Answer
  1. $\frac{5\pi}{6}$
$\cos^{-1}\bigg(\cos\frac{7\pi}{6}\bigg)=\cos^{-1}\bigg[\cos\bigg(2\pi-\frac{7\pi}{6}\bigg)\bigg]$
$\left[\because\cos\left(2\pi-\theta\right)=\cos\theta\right]$
$=2\pi-\frac{7\pi}{6}=\frac{12\pi-7\pi}{6}=\frac{5\pi}{6}$
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1 Marks Question - Page 2 - MATHS STD 12 Science Questions - Vidyadip