If $\sec \theta \sqrt{2}$ and $\theta$ lies in Quadrant IV, find the values of all the other five trigonometric functions.
Given: $\sec \theta=\sqrt{2}$
Since, $\theta$ is in IV th Quadrant. So, sin and tan will be negative but $\cos$ will be positive.
Now, we know that
$\cos \theta=\frac{1}{\sec \theta}$
Putting the values, we get
$\cos \theta=\frac{1}{\sqrt{2}}$ …(i)
We know that,
$\cos ^{2} \theta+\sin ^{2} \theta=1$
Putting the values, we get
$\left(\frac{1}{\sqrt{2}}\right)^{2}+\sin ^{2} \theta=1$ [Given]
$\Rightarrow \frac{1}{2}+\sin ^{2} \theta=1$
$\Rightarrow \sin ^{2} \theta=1-\frac{1}{2}$
$\Rightarrow \sin ^{2} \theta=\frac{2-1}{2}$
$\Rightarrow \sin ^{2} \theta=\frac{1}{2}$
$\Rightarrow \sin \theta=\sqrt{\frac{1}{2}}$
$\Rightarrow \sin \theta=\pm \frac{1}{\sqrt{2}}$
Since, $\theta$ in IV $^{\text {th }}$ quadrant and $\sin \theta$ is negative in IV $^{\text {th }}$ quadrant
$\therefore \sin \theta=-\frac{1}{\sqrt{2}}$
Now,
$\tan \theta=\frac{\sin \theta}{\cos \theta}$
Putting the values, we get
$\tan \theta=\frac{-\frac{1}{\sqrt{2}}}{\frac{1}{\sqrt{2}}}$
$=-\frac{1}{\sqrt{2}} \times(\sqrt{2})$
$=-1$
Now,
$\operatorname{cosec} \theta=\frac{1}{\sin \theta}$
Putting the values, we get
$\operatorname{cosec} \theta=\frac{1}{-\frac{1}{\sqrt{2}}}$
$=-\sqrt{2}$
Now
$\cot \theta=\frac{1}{\tan \theta}$
Putting the values, we get
$\cot \theta=\frac{1}{-1}$
$=-1$
Hence, the values of other trigonometric Functions are: