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How to find cos theta?

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How to find cos theta?

Guest Mar 4, 2018
#1
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You'll just have to use a calculator   to find   cos (-3/2 degrees) = .999657

or if you need   cos ( -3/2 radians) = .070737

ElectricPavlov  Mar 4, 2018
#3
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You got in a mess with this one EP

But considering how may questions you answer correctly I do not think you need to be upset by a silly error here and there. :)

Melody  Mar 4, 2018
#2
+93346
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$$tan \theta = -\frac{3}{2}\\$$

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Think about   $$tan \theta = +\frac{3}{2}$$    first

Draw a right angled triangle.

Mark an acute angle as theta.

opp = 3

so hypotenuse  =     $$\sqrt{9+4}=\sqrt{13}$$

So for this triangle   $$cos\theta= \frac{2}{\sqrt{13}}=\frac{2\sqrt{13}}{13}$$

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Now, tan is negative in the 2nd and 4th quadrant

In the 2nd quad Cos is negative and in the 4th quad Cos is positive.

So

$$cos\theta=\pm\frac{2\sqrt{13}}{13}$$

Melody  Mar 4, 2018