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PLEASE HELP PLEASE HELP ASAP ASAP .

PLEASE HELP PLEASE HELP ASAP ASAP .-example-1
User Wazza
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1 Answer

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Answer:


\cos^(-1) (-(√(2) )/(2)) = 135^\circ

Explanation:

Let us assume that
\theta = \cos^(-1) (-(√(2) )/(2))


\cos \theta = -(√(2) )/(2) = - (1)/(√(2) ) ........... (1)

So, the
\cos \theta value is negative in the second and third quadrant and we know that
\cos 45 = (1)/(√(2)).

Therefore,
\theta = \pi + (\pi )/(4) or
\theta = \pi - (\pi )/(4)

And the general solution of equation (1) is given by


\theta = (2n + 1)\pi \pm (\pi )/(4) for n = 0, 1, 2, ....

Since we need a definite solution of
\theta in the second quadrant, hence,
\theta = \pi  - (\pi )/(4) = 135^\circ. (Answer)

User Ricovitch
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