```ts
/** a divided by b. Throws error on illegal input */
export function safeDivide(a: number, b: number): number {
  if (typeof a !== "number" || typeof b !== "number") {
    throw new Error('Both arguments must be numbers');
  }
  
  if (!isFinite(a) || !isFinite(b)) {
    throw new Error('Both arguments must be finite numbers');
  }
  
  if (b === 0 || b === -0) {
    throw new Error('Cannot divide by zero');
  }
  
  return a / b;
}
```