Question

Cubul ABCDA'B'C'D' are AB=12 cm. Aflati masura unghiului (AC;BC')​

Answer 1

$\it A'C'||AC\ \Rightarrow \widehat{AC,\ BC'}=\widehat{A'C',\ BC'}=60^o,\ deoarece\ \Delta BC'A'-echilateral$