Question

Q. Find the value of Cos (11π÷6).
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Answer 1

cos(11π/6)=cos(2π-π/6)

=cos(π/6)

=√3/2

Answer 2

Answer:

Required value is 0.8660254.

Step-by-step explanation:

This is a problem of Trigonometry.

For solving this question we should know all degree values of Trigonometry.

We know, using radian to degree conversation,

$\theta$in degrees$= \theta$in radians $\times \frac{ {180}^{o} }{\pi}$

So,

$\frac{11\pi}{6} \: radians = \frac{11\pi}{6} \times \frac{ {180}^{o} }{\pi} = {330}^{o}$

Hence,

$cos \frac{11\pi}{6} = \cos( {330}^{o} ) = \frac{ \sqrt{3} }{2} \: or \: 0.8660254$

Therefore required value is 0.8660254.

Some important degree values of Cos,

$\cos( {0}^{o} ) = 1 \\ \cos( {30}^{o} ) = \frac{ \sqrt{3} }{2} \\ \cos( {45}^{o} ) = \frac{1}{ \sqrt{2} } \\ \cos( {60}^{o} ) = \frac{1}{2} \\ \cos( {90}^{o} ) = 0$