Explanations 
Textbooks 
Flashcards 
91影视 AI 
Notes 
Study Plans 
Study Sets 
Find a degree 
Magazine Problem 777
Show if a plane intersects a sphere, the intersection is a circle.
Problem 784
Show that if a plane intersects two parallel planes, then it intersects them in two parallel lines.
Problem 792
Show that parallel planes are everywhere equidistant.
Problem 795
If two planes are perpendicular to each other, prove that a line drawn in one of them perpendicular to their intersection is perpendicular to the other plane.
Problem 799
Show that two lines perpendicular to the same plane are parallel.
Problem 805
Show that the sum of the measures of the face angles of any convex polyhedral angle is less than \(360^{\circ}\). An informal argument will suffice.
Problem 808
The lateral edges of a prism are congruent and parallel. Prove this.
Problem 809
Show that every section of a prism made by a plane parallel to the bases is congruent to the bases.
Problem 810
In a regular square pyramid, the length of each side of the square base is 12 in., and the length of the altitude is 8 in. (a) Find the length of the slant height of the pyramid (b) Find, in radical form, the length of the lateral edge of the
Problem 811
Show that the lateral edges of a regular pyramid are congruent.
