U trokutu ABCABCABC vrijedi ∣BC∣+∣AC∣=2∣AB∣|BC| + |AC| = 2|AB|∣BC∣+∣AC∣=2∣AB∣ i ∡BAC−∡CBA=90∘\measuredangle BAC - \measuredangle CBA = 90^\circ∡BAC−∡CBA=90∘.
Odredi kosinus kuta ∡ACB\measuredangle ACB∡ACB.