Eliminate $\theta$ from these two equations

inverse functiontrigonometry

If $$\operatorname{cosec}\theta-\operatorname{sin}\theta=m$$ and $$\operatorname{sec}\theta-\operatorname{cos}\theta=n$$ then eliminate $\theta$.

My work:

Squaring both the equations and then adding them will yeild $$\operatorname{cosec}^2\theta+\operatorname{sec}^2\theta=m^2+n^2+3$$ or
$$\operatorname{cos}^2\theta\operatorname{sin}^2\theta=\frac{1}{m^2+n^2+3}$$ or$$\operatorname{sin}^2 2\theta=\frac{4}{m^2+n^2+3}$$ or
$$\theta=\frac12\cdot\operatorname{arcsin}\left(\frac{2}{\sqrt{m^2+n^2+3}}\right)$$
Now to eliminate $\theta$, we will have to put its value in any of the two equations.

But actually I don't know how to evaluate inverse trigonometric values, like that of $\theta$ in terms of $m$ and $n$. And after that I guess it will be difficult to simplify the expression.

Any help is greatly appreciated.

Best Answer

Writing $x$ for $\theta,$

$$m=\csc x-\sin x=\dfrac{\cos^2x}{\sin x}$$

$$\text{Similarly, } n=\sec x-\cos x=\dfrac{\sin^2x}{\cos x}$$

$$\dfrac mn=\dfrac{\cos^3x}{\sin^3x} \implies\dfrac m{\cos^3x}=\dfrac n{\sin^3x}=\dfrac{m^{2/3}+n^{2/3}}1$$

Replacing the values of $\cos x,\sin x;$

$$ m=\dfrac{\left(\dfrac m{m^{2/3}+n^{2/3}}\right)^{2/3}}{\left(\dfrac n{m^{2/3}+n^{2/3}}\right)^{1/3}} \implies m(m^{2/3}+n^{2/3})^{1/3}n^{1/3}=m^{2/3}$$

Now I leave the rest for the OP

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