# Synopsis

PDX_MSGT gdx_EvalArcDerivs(long option, T_GDX_ARC *gdx_arc, int max_deriv, double tval, double (*derivs)[3])

# Purpose

Evaluate derivatives on a GDX conic curve

# Description

For a give S parameter value, evaluates the requested derivatives on a GDX arc. The tval parameter values is the unnormalized arc parameter value by default. A max_deriv > 4 returns 0.0 derivative values.

# Input

## option

### GDX_UNNORM

Unnormalize the parameter value

## gdx_arc

The GDX arc curve data structure

## max_deriv

The maximium deriviative desired

## tval

The parameter value

# Output

## derivs

The 3D deriviatives

# Return

          GDX_NOERR
          GDX_PARMOUTOFRANGE
          .fi