What is the value of cos(60)*15 ?

The value of cos(60)*15 is 15/2

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cos(60)*15

cos (6 0^{\circ}) \cdot 15

\frac{15}{2}

Decimal Notation

7.5

Solution steps

cos (6 0^{\circ}) \cdot 15

Use the following trivial identity:

cos (6 0^{\circ}) = \frac{1}{2}

cos (6 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{1}{2}

= \frac{1}{2} \cdot 15

Simplify

\frac{1}{2} \cdot 15 : \frac{15}{2}

\frac{1}{2} \cdot 15

Convert element to fraction:

15 = \frac{15}{1}

= \frac{1}{2} \cdot \frac{15}{1}

Multiply fractions:

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

= \frac{1 \cdot 15}{2 \cdot 1}

Cancel the common factor:

1

= \frac{15}{2}

= \frac{15}{2}

2 sec^{2} (4 5^{\circ}) sec (3 0^{\circ}) - 3 cos (6 0^{\circ}) tan (6 0^{\circ})

\frac{1}{arctan ( \frac{3}{4} )}

sin^{2} (4 5^{\circ}) + 8 cos^{2} (3 0^{\circ})

cos (0.6593)

tan (3 0^{\circ}) tan (6 0^{\circ})