Question 1203975
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In the post by @MathLover1, part of her solution (part of her writing) is incorrect.  

In my post, I deleted/removed incorrect parts of her solution and saved only that lines that are correct.



<pre>
    {{{ sec^2(theta) -2=0 }}},  {{{ -pi< theta <pi}}}

    {{{sec^2(theta)}}} = 2.

    {{{sec(theta)}}} = +/- {{{sqrt(2)}}}


Solutions in given interval {{{-pi}}} < {{{theta}}} < {{{pi}}}

    {{{sec(theta)}}} = {{{sqrt(2)}}} ==> {{{theta}}}  = {{{pi/4}}}  or  {{{theta}}} = {{{-pi/4 }}}.

    {{{sec(theta)}}} = {{{-sqrt(2)}}} ==>  {{{theta}}} = {{{3pi/4}}}  or  {{{theta}}} = {{{-3pi/4}}}.


<U>ANSWER</U>.  {{{theta}}} = {{{pi/4}}}, {{{-pi/4 }}}, {{{3pi/4}}}, {{{-3pi/4}}}.
</pre>