5.3.1.17 Construction of secrets

Condition: Build the sector of the prism \ (a b c a_ {1} b_ {1} c_ {1} \) with the plane set by points \ (p, q \) and \ (r. P \) lies in the face \ (a_ {1} b_ {1} b, q \) lies on the rib \ (a c \), \ (r \) Lies in the granium \ (b b_ {1} c_ {1} c \).