91Ó°ÊÓ

In the following diagram$\stackrel{¯}{HL}$ and$\stackrel{↔}{KT}$ intersect at the midpoint of $\stackrel{¯}{HL}$. Classify the following statement as true or false.

$\stackrel{↔}{KT}$is a bisector of $\stackrel{¯}{LH}$.

Given the diagram, tell whether you can reach the conclusion shown.

Name three collinear points.

Sketch and label the figures described.

Planes$X$and$Y$intersect in $\stackrel{↔}{AB}$.

Which of the four things stated can’t you conclude from the diagram?

1. $\mathbf{A}$,$\mathbf{B}$and$\mathbf{C}$are collinear.
2. $\mathbf{∠}\mathbf{DBC}$Is a right angle.
3. $\mathbf{B}$is the midpoint of $\stackrel{↔}{\mathrm{AC}}$.
4. $\mathbf{E}$is in the interior of $\mathbf{∠}\mathbf{DBA}$.

In Exercises 5-11 you will have to visualize certain lines and planes not shown in the diagram of the box. When you name a plane, name it by using four points, no three of which are collinear.

Name the intersection of plane$\mathbf{DCFE}$ and plane $\mathbf{ABCD}$.

State whether the angle appears to be acute, right, obtuse, or straight. Then estimate its measure.

• $∠EDB$
  

In Exercises 5-11 you will have to visualize certain lines and planes not shown in the diagram of the box. When you name a plane, name it by using four points, no three of which are collinear.

Name four lines shown in the diagram that don’t intersect plane EFGH.

State a postulate, or part of a postulate, that justifies your answer to each exercise.

Name three points that determine plane M.

Classify each statement as true or false.

A,B, and C are collinear.

Can a given point be in two lines? In ten lines?