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I really need help solving this practice from my prep guide in trigonometryI don’t know why but I have a hard time solving it completely

I Really Need Help Solving This Practice From My Prep Guide In TrigonometryI Dont Know Why But I Have A Hard Time Solving It Completely class=

Sagot :

Given:

[tex]\frac{\tan(-\frac{2\pi}{3})}{\sin(\frac{7\pi}{4})}-\sec (-\pi)[/tex]

First

Recall

[tex]\sec (\pi)=\frac{1}{\cos (\pi)}[/tex]

This implies

[tex]\sec (-\pi)=\frac{1}{\cos (-\pi)}[/tex]

Hence, the given expression becomes

[tex]\frac{\tan(-\frac{2\pi}{3})}{\sin(\frac{7\pi}{4})}-\frac{1}{\cos (-\pi)}[/tex]

Using calculator

[tex]\cos (-\pi)=-1[/tex]

Hence,

[tex]\begin{gathered} \frac{\tan(-\frac{2\pi}{3})}{\sin(\frac{7\pi}{4})}-\frac{1}{\cos (-\pi)} \\ =\frac{\tan(-\frac{2\pi}{3})}{\sin(\frac{7\pi}{4})}-\frac{1}{-1} \\ =\frac{\tan(-\frac{2\pi}{3})}{\sin(\frac{7\pi}{4})}+1 \end{gathered}[/tex]

Also,

[tex]\sin (\frac{7\pi}{4})=-\frac{1}{\sqrt[]{2}}[/tex]

This gives

[tex]\begin{gathered} \frac{\tan(-\frac{2\pi}{3})}{\sin(\frac{7\pi}{4})}+1 \\ =\frac{\tan(-\frac{2\pi}{3})}{-\frac{1}{\sqrt[]{2}}}+1 \end{gathered}[/tex]

Simplifying the expression gives

[tex]\begin{gathered} \frac{\tan(-\frac{2\pi}{3})}{-\frac{1}{\sqrt[]{2}}}+1 \\ =\tan (-\frac{2\pi}{3})\div-\frac{1}{\sqrt[]{2}}+1 \\ =\tan (-\frac{2\pi}{3})\times-\sqrt[]{2}+1 \\ =-\sqrt[]{2}\tan (-\frac{2\pi}{3})+1 \end{gathered}[/tex]

Using the following property

[tex]\tan (-x)=-\tan (x)[/tex]

It follows

[tex]\tan (-\frac{2\pi}{3})=-\tan (\frac{2\pi}{3})[/tex]

Hence the expression becomes

[tex]\begin{gathered} -\sqrt[]{2}\tan (-\frac{2\pi}{3})+1 \\ =-\sqrt[]{2}(-\tan (\frac{2\pi}{3}))+1 \\ =\sqrt[]{2}\tan (\frac{2\pi}{3})+1 \end{gathered}[/tex]

And

[tex]\tan (\frac{2\pi}{3})=-\sqrt[]{3}[/tex]

This gives

[tex]\begin{gathered} \sqrt[]{2}\tan (-\frac{2\pi}{3})+1 \\ =\sqrt[]{2}(-\sqrt[]{3)}+1 \end{gathered}[/tex]

Simplifying the expression gives

[tex]\begin{gathered} \sqrt[]{2}(-\sqrt[]{3)}+1 \\ =-\sqrt[]{6}+1 \end{gathered}[/tex]

Therefore, the answer is

[tex]-\sqrt[]{6}+1[/tex]

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