the principal value of cos 1 1sqrt 2 cos 9pi 10 sin 9pi 10

The principal value of $${\cos ^{ - 1}}\left\{ {\frac{1}{{\sqrt 2 }}\left( {\cos\frac{{9\pi }}{{10}} - \sin \frac{{9\pi }}{{10}}} \right)} \right\}$$ is

A. $$\frac{{3\pi }}{{20}}$$

B. $$\frac{{7\pi }}{{20}}$$

C. $$\frac{{7\pi }}{{10}}$$

D. None of these

Answer : None of these

Solution :
$$\eqalign{ & \frac{1}{{\sqrt 2 }}\left( {\cos\frac{{9\pi }}{{10}} - \sin \frac{{9\pi }}{{10}}} \right) = \cos \left( {\frac{\pi }{4} + \frac{{9\pi }}{{10}}} \right). \cr & \frac{1}{{\sqrt 2 }}\left( {\cos\frac{{9\pi }}{{10}} - \sin \frac{{9\pi }}{{10}}} \right) = \cos \frac{{23\pi }}{{20}} = \cos \left( {2\pi - \frac{{23\pi }}{{20}}} \right) = \cos \frac{{17\pi }}{{20}} \cr} $$
∴ the value $$ = {\cos ^{ - 1}}\left( {\cos \frac{{17\pi }}{{20}}} \right) = \frac{{17\pi }}{{20}}$$

Releted MCQ Question on
Trigonometry >> Inverse Trigonometry Function

Releted Question 1

The value of $$\tan \left[ {{{\cos }^{ - 1}}\left( {\frac{4}{5}} \right) + {{\tan }^{ - 1}}\left( {\frac{2}{3}} \right)} \right]$$ is

A. $$\frac{6}{{17}}$$

B. $$\frac{7}{{16}}$$

C. $$\frac{16}{{7}}$$

D. none

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Releted Question 2

If we consider only the principle values of the inverse trigonometric functions then the value of $$\tan \left( {{{\cos }^{ - 1}}\frac{1}{{5\sqrt 2 }} - {{\sin }^{ - 1}}\frac{4}{{\sqrt {17} }}} \right)$$ is

A. $$\frac{{\sqrt {29} }}{3}$$

B. $$\frac{{29}}{3}$$

C. $$\frac{{\sqrt {3}}}{29}$$

D. $$\frac{{3}}{29}$$

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Releted Question 3

The number of real solutions of $${\tan ^{ - 1}}\sqrt {x\left( {x + 1} \right)} + {\sin ^{ - 1}}\sqrt {{x^2} + x + 1} = \frac{\pi }{2}$$ is

A. zero

B. one

C. two

D. infinite

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Releted Question 4

If $${\sin ^{ - 1}}\left( {x - \frac{{{x^2}}}{2} + \frac{{{x^3}}}{4} - .....} \right) + {\cos ^{ - 1}}\left( {{x^2} - \frac{{{x^4}}}{2} + \frac{{{x^6}}}{4} - .....} \right) = \frac{\pi }{2}$$ for $$0 < \left| x \right| < \sqrt 2 ,$$ then $$x$$ equals

A. $$ \frac{1}{2}$$

B. 1

C. $$ - \frac{1}{2}$$

D. $$- 1$$

View Answer

The principal value of $${\cos ^{ - 1}}\left\{ {\frac{1}{{\sqrt 2 }}\left( {\cos\frac{{9\pi }}{{10}} - \sin \frac{{9\pi }}{{10}}} \right)} \right\}$$ is

Releted MCQ Question on
Trigonometry >> Inverse Trigonometry Function

The value of $$\tan \left[ {{{\cos }^{ - 1}}\left( {\frac{4}{5}} \right) + {{\tan }^{ - 1}}\left( {\frac{2}{3}} \right)} \right]$$ is

If we consider only the principle values of the inverse trigonometric functions then the value of $$\tan \left( {{{\cos }^{ - 1}}\frac{1}{{5\sqrt 2 }} - {{\sin }^{ - 1}}\frac{4}{{\sqrt {17} }}} \right)$$ is

The number of real solutions of $${\tan ^{ - 1}}\sqrt {x\left( {x + 1} \right)} + {\sin ^{ - 1}}\sqrt {{x^2} + x + 1} = \frac{\pi }{2}$$ is

If $${\sin ^{ - 1}}\left( {x - \frac{{{x^2}}}{2} + \frac{{{x^3}}}{4} - .....} \right) + {\cos ^{ - 1}}\left( {{x^2} - \frac{{{x^4}}}{2} + \frac{{{x^6}}}{4} - .....} \right) = \frac{\pi }{2}$$ for $$0 < \left| x \right| < \sqrt 2 ,$$ then $$x$$ equals

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The principal value of $${\cos ^{ - 1}}\left\{ {\frac{1}{{\sqrt 2 }}\left( {\cos\frac{{9\pi }}{{10}} - \sin \frac{{9\pi }}{{10}}} \right)} \right\}$$ is

Releted MCQ Question on Trigonometry >> Inverse Trigonometry Function

The value of $$\tan \left[ {{{\cos }^{ - 1}}\left( {\frac{4}{5}} \right) + {{\tan }^{ - 1}}\left( {\frac{2}{3}} \right)} \right]$$ is

If we consider only the principle values of the inverse trigonometric functions then the value of $$\tan \left( {{{\cos }^{ - 1}}\frac{1}{{5\sqrt 2 }} - {{\sin }^{ - 1}}\frac{4}{{\sqrt {17} }}} \right)$$ is

The number of real solutions of $${\tan ^{ - 1}}\sqrt {x\left( {x + 1} \right)} + {\sin ^{ - 1}}\sqrt {{x^2} + x + 1} = \frac{\pi }{2}$$ is

If $${\sin ^{ - 1}}\left( {x - \frac{{{x^2}}}{2} + \frac{{{x^3}}}{4} - .....} \right) + {\cos ^{ - 1}}\left( {{x^2} - \frac{{{x^4}}}{2} + \frac{{{x^6}}}{4} - .....} \right) = \frac{\pi }{2}$$ for $$0 < \left| x \right| < \sqrt 2 ,$$ then $$x$$ equals

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Releted MCQ Question on
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