Evaluate
2\sqrt{2}\approx 2.828427125
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4\cos(2\times \frac{1}{8}\pi )
Divide 3\pi by 24 to get \frac{1}{8}\pi .
4\cos(\frac{1}{4}\pi )
Multiply 2 and \frac{1}{8} to get \frac{1}{4}.
4\times \frac{\sqrt{2}}{2}
Get the value of \cos(\frac{1}{4}\pi ) from trigonometric values table.
2\sqrt{2}
Cancel out 2, the greatest common factor in 4 and 2.
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