```typescript
/**
 * a divided by b.
 */
export function safeDivide(a: number, b: number): number {
  if (typeof a !== 'number' || typeof b !== 'number') {
    throw new Error('Both arguments must be numbers.');
  }
  if (!Number.isFinite(a) || !Number.isFinite(b)) {
    throw new Error('Arguments must be finite numbers.');
  }
  if (b === 0 || b === -0) {
    throw new Error('Divisor cannot be zero.');
  }
  return a / b;
}
```