What is the value of cos(-(13pi)/6) ?

The value of cos(-(13pi)/6) is (sqrt(3))/2

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cos(-(13pi)/6)

cos (- \frac{13 π}{6})

\frac{3}{2}

Decimal Notation

0.86602 \dots

Solution steps

cos (- \frac{13 π}{6})

Use the following property:

cos (- x) = cos (x)

cos (- \frac{13 π}{6}) = cos (\frac{13 π}{6})

= cos (\frac{13 π}{6})

cos (\frac{13 π}{6}) = cos (\frac{π}{6})

cos (\frac{13 π}{6})

Rewrite

\frac{13 π}{6}

2 π + \frac{π}{6}

= cos (2 π + \frac{π}{6})

Apply the periodicity of

cos

cos (x + 2 π) = cos (x)

cos (2 π + \frac{π}{6}) = cos (\frac{π}{6})

= cos (\frac{π}{6})

= cos (\frac{π}{6})

Use the following trivial identity:

cos (\frac{π}{6}) = \frac{3}{2}

cos (\frac{π}{6})

cos (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= \frac{3}{2}

= \frac{3}{2}

sec (π) tan (π)

arctan (\frac{9}{4})

arctan (\frac{9}{5})

sin (arcsin (π))

arccos (- 0.7)

What is the value of cos(-(13pi)/6) ?
The value of cos(-(13pi)/6) is (sqrt(3))/2