What is the value of -cos(-2pi) ?

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-cos(-2pi)

- cos (- 2 π)

- 1

Solution steps

- cos (- 2 π)

Rewrite using trig identities:

cos (- 2 π) = 1

cos (- 2 π)

Use the following property:

cos (- x) = cos (x)

cos (- 2 π) = cos (2 π)

= cos (2 π)

cos (2 π) = cos (0)

cos (2 π)

Rewrite

2 π

2 π + 0

= cos (2 π + 0)

Apply the periodicity of

cos

cos (x + 2 π) = cos (x)

cos (2 π + 0) = cos (0)

= cos (0)

= cos (0)

Use the following trivial identity:

cos (0) = 1

cos (0)

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}

= 1

= 1

= - 1

csc (8 0^{\circ})

\frac{cos ( - 0.01 ) - 1}{- 0.01}

cos (arctan (- 6))

arctan (3.5)

cos (\frac{0}{2})