What is the value of 8cos(90) ?

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8cos(90)

8 cos (9 0^{\circ})

0

Solution steps

8 cos (9 0^{\circ})

Use the following trivial identity:

cos (9 0^{\circ}) = 0

cos (9 0^{\circ})

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}

= 0

= 8 \cdot 0

Simplify

= 0

tan (\frac{24}{7})

cos (\frac{5 π}{3}) cos (\frac{π}{6}) - sin (\frac{5 π}{3}) sin (\frac{π}{6})

arctan (\frac{3}{3})

- \frac{3 sin ( 2 )}{2 3 cos ( 2 ) + 10}

tan (10 6^{\circ})