Explanation
We need to find value of $$\sin ^{ -1 }{ \left( \dfrac { 2\sqrt { 2 } }{ 3 } \right) } +\sin ^{ -1 }{ \left( \dfrac { 1 }{ 3 } \right) } $$
Let $$\sin ^{ -1 }{ \left( \dfrac { 2\sqrt { 2 } }{ 3 } \right) } =t$$
$$\Rightarrow \sin { t } =\dfrac { 2\sqrt { 2 } }{ 3 } \\ \sin ^{ 2 }{ t } +\cos ^{ 2 }{ t } =1\\ { \left( \dfrac { 2\sqrt { 2 } }{ 3 } \right) }^{ 2 }+\cos ^{ 2 }{ t } =1\\ \Rightarrow \cos ^{ 2 }{ t } =\dfrac { 1 }{ 9 } \\ \Rightarrow \cos { t } =\dfrac { 1 }{ 3 } \\ \Rightarrow t=\cos ^{ -1 }{ \left( \dfrac { 1 }{ 3 } \right) } $$
Substituting $$t$$
$$\Rightarrow \cos ^{ -1 }{ \left( \dfrac { 1 }{ 3 } \right) } +\sin ^{ -1 }{ \left( \dfrac { 1 }{ 3 } \right) } \\ =\dfrac { \pi }{ 2 } $$
So, option C is correct.
Given that ,$$f\left( x \right)={{\tan }^{-1}}x$$ ….(1)
Put x=y in equation (1) we get
$$f\left( y \right)={{\tan }^{-1}}y$$ ….(2)
Add equation (1) and (2)
$$f\left( x \right)+f\left( y \right)={{\tan }^{-1}}x+{{\tan }^{-1}}y$$
Using inverse trigonometry properties, we get
$${{\tan }^{-1}}x+{{\tan }^{-1}}y$$ $$={{\tan }^{-1}}\left( \dfrac{x+y}{1-xy} \right)$$
We have,
$$ {{\sin }^{-1}}\left( \cos x \right) $$
$$ ={{\sin }^{-1}}\left( \sin \left( \dfrac{\pi }{2}-x \right) \right) $$
$$ =\dfrac{\pi }{2}-x\,\,\,\,\,\,\,\,\,\,\,\, $$
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