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Popular >

cos(720)

Solution

cos (72 0^{\circ})

Solution

1

Solution steps

cos (72 0^{\circ})

cos (72 0^{\circ}) = cos (0)

cos (72 0^{\circ})

Rewrite

72 0^{\circ}

as

36 0^{\circ} \cdot 2 + 0

= cos (36 0^{\circ} 2 + 0)

Apply the periodicity of

cos

:

cos (x + 36 0^{\circ} \cdot k) = cos (x)

cos (36 0^{\circ} \cdot 2 + 0) = cos (0)

= cos (0)

= cos (0)

Use the following trivial identity:

cos (0) = 1

cos (0)

cos (x)

periodicity table with

36 0^{\circ} n

cycle:

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= 1

= 1

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Frequently Asked Questions (FAQ)

What is the value of cos(720) ?
The value of cos(720) is 1