Function pendulum

pendulum(
    params?: {
        b?: number;
        g?: number;
        L?: number;
        tau?: (t: number) => number;
    },
): ChalkboardODE
Defines a pendulum (nonlinear) with optional damping and external torque: θ'' + (b)θ' + (g/L)sin(θ) = τ(t). Equivalent: θ'' = τ(t) - bθ' - (g/L)sin(θ).
Parameters
- params: { b?: number; g?: number; L?: number; tau?: (t: number) => number } = {}
  - Optionalb?: number
    
    Damping coefficient
  - Optionalg?: number
    
    Gravity (greater than or equal to 0)
  - OptionalL?: number
    
    Length (non-zero)
  - Optionaltau?: (t: number) => number
    
    External torque τ(t) (0 by default)
Returns ChalkboardODE
Example
```
const ode = Chalkboard.diff.pendulum({ L: 2, g: 9.81 });
const acceleration = ode.rule(0, [Chalkboard.PI(1 / 2), 0]); // Evaluates a simple pendulum
```
- Defined in Chalkboard.diff.ts:556