Determine the exact value for cos^-1(cos(7π/6)).
...& Also...
Determine the value of cos(-7π/4).

Question

Determine the exact value for cos^-1(cos(7π/6)).
...& Also...
Determine the value of cos(-7π/4).

anonymous · Answer

Well $$\Large \cos (\cos^{-1} (x))$$

anonymous · Answer

=$$\Large x$$

anonymous · Answer

$$\Large \cos(-x)=\cos(x)=\cos(-\frac{7\pi}{4})=\cos(\frac{7\pi}{4})$$

anonymous · Answer

You can proceed from there right?

kainui · Answer

Since cos^-1() is the inverse function of cos(), you're just undoing it. It's like squaring the square root function, you get back what's inside.

To find the value of cos(-7π/4) you should realize that cosine is basically looking for the x-value of rotation on a circle and that a circle has 2π radians in all.

since they say -7π/4, that means you rotate around clockwise because of the negative sign for 7 quarters of pi.

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