# Calculate cosine in degrees

I'd like to calculate the value of the cosine of 52 degrees. The following fails:

```
lam = 52 * sage.units.degree
cos(lam)
```

How should I do it correctly?

Calculate cosine in degrees

I'd like to calculate the value of the cosine of 52 degrees. The following fails:

```
lam = 52 * sage.units.degree
cos(lam)
```

How should I do it correctly?

add a comment

1

A degree is easily converted in radian (360° versus $2\pi$)

```
sage: cos(52 / 360 * (2*pi))
cos(13/45*pi)
```

While this is perfectly correct, this is not very useful. In order to get a numerical approximation you can do

```
sage: c = cos(52 / 360 * (2*pi))
sage: c.numerical_approx()
0.615661475325658
```

1

@kcrisman: I agree with you but there is no such module as sage.units

Perhaps the OP was using http://doc.sagemath.org/html/en/refer... ?

Right. Then it is `units.angles.degree`

and `units.angles.radian`

which ends up in error in evaluations

```
sage: s = 2 * units.angles.radian
sage: s.cos()
cos(2*radian)
sage: _.n()
Traceback (most recent call last):
...
TypeError: cannot evaluate symbolic expression numerically
```

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Asked: ** 2016-01-06 14:50:53 +0200 **

Seen: **2,455 times**

Last updated: **Jan 06 '16**

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