Question 91
The cube $ABCD'A'B'C'D'$ has edges of length $a$. Take the points $E \in (AB)$ and $F \in (BC)$ so that $AE + CF = EF$.
a) Find the measure of the angle of the planes $(D'DE)$ and $(D'DF)$.
b) Compute the distance from $D'$ to the straight line $EF$.
a) Find the measure of the angle of the planes $(D'DE)$ and $(D'DF)$.
b) Compute the distance from $D'$ to the straight line $EF$.