Trigonometrische Gleichungen lösen #3d: alle Lösungen im Intervall (ohne TR, Kosinus)

How to Math video overview at https://howtomathe.de Another example of a cosine without a calculator. As usual, you first calculate an arbitrary solution, then the period length (although this example requires a bit of fractional arithmetic), and then use a diagram to determine the other solutions. Just like with sine, you need to know where the cosine becomes 0, 1, or -1. It's best to learn this by memorizing the basic diagram!