[`ln(-1) = πi`](https://www.google.com/search?q=ln+-1&oq=ln+-1&aqs=chrome.0.69i59.1105j0j1&sourceid=chrome&ie=UTF-8) [`sqrt(-4) = 2i`](https://www.google.com/search?q=sqrt+-4&oq=sqrt+-4&aqs=chrome.0.69i59.1799j0j1&sourceid=chrome&ie=UTF-8)