What is the value of cos(120)+cos(45) ?

The value of cos(120)+cos(45) is (-1+sqrt(2))/2

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cos(120)+cos(45)

cos (12 0^{\circ}) + cos (4 5^{\circ})

\frac{- 1 + 2}{2}

Solution steps

cos (12 0^{\circ}) + cos (4 5^{\circ})

Use the following trivial identity:

cos (12 0^{\circ}) = - \frac{1}{2}

Use the following trivial identity:

cos (4 5^{\circ}) = \frac{2}{2}

= - \frac{1}{2} + \frac{2}{2}

Simplify

- \frac{1}{2} + \frac{2}{2} : \frac{- 1 + 2}{2}

= \frac{- 1 + 2}{2}

cos (11 5^{\circ})

2 sin (2 π)

3 cos (3 0^{\circ})

π cos (π)

- cot (\frac{π}{2})

What is the value of cos(120)+cos(45) ?
The value of cos(120)+cos(45) is (-1+sqrt(2))/2