PI
PI(π)の値を返します。
フォーマット
PI例
<Force_Scalar_TwoBody
id = "32"
type = "Force"
i_marker_id = "175"
body1_id = "31"
j_marker_id = "176"
body2_id = "35"
val_expression = "100*PI " >
</Force_Scalar_TwoBody>