What is the value of 981cos(30) ?

The value of 981cos(30) is (981sqrt(3))/2

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981cos(30)

981 cos (3 0^{\circ})

\frac{981 3}{2}

Decimal Notation

849.57092 \dots

Solution steps

981 cos (3 0^{\circ})

Use the following trivial identity:

cos (3 0^{\circ}) = \frac{3}{2}

cos (3 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}

= \frac{3}{2}

= 981 \cdot \frac{3}{2}

Simplify

981 \cdot \frac{3}{2} : \frac{981 3}{2}

981 \cdot \frac{3}{2}

Multiply fractions:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{3 \cdot 981}{2}

= \frac{981 3}{2}

\frac{1 + cos ( 7 5 ^{\circ} )}{2}

4 1 + cos^{2} (\frac{7 π}{32})

450 cos (- 2 4^{\circ})

sin^{2} (\frac{\frac{π}{3}}{2})

- 8 cos (\frac{1}{2} ((4.731) + \frac{π}{3})) - 4.731