# THETA

The THETA function computes the second angle, in radians, of a body-2
Euler angle rotation sequence (body-3, body-1, body-3) of marker `I` with
respect to marker `J`.

## Format

THETA(I, J)## Arguments

`I`- The marker whose rotational displacement is to be computed. Must be specified.
`J`- The marker with respect to which the rotational displacement is to be computed. This argument is optional. If omitted, it defaults to the ground coordinate system.

## Example

```
<Motion_Joint
id = "301001"
type = "EXPRESSION"
val_type = "D"
expr = "STEP5(TIME,.2,0,.4,180D)"
joint_id = "10010"
joint_type = "R"
/>
```