91Ó°ÊÓ

Write the name or statement of the definition, postulate, or theorem that justifies the statement about the diagram.

$∠2â‰\dots ∠6$

Complete. You may find that drawing a diagram will help you.

If point Blies in the interior of$∠AOC$, then$mâˆ$___?___+$mâˆ$___?___=$mâˆ$___?___.

Use the conditional: If $m∠1=120$, then∠1 is obtuse.

Provide a counterexample to disprove the converse.

a. In each exercise use the information given to conclude that two angles are congruent.

b. Name or state the definition or theorem that justifies your conclusion.

$\stackrel{\mathbf{¯}}{\mathbf{AB}}\mathbf{âŠ\yen }\stackrel{\mathbf{¯}}{\mathbf{CD}}$

For exercises 3 and 4 you are given that $\stackrel{\mathbf{→}}{\mathbf{OB}}\mathbf{âŠ\yen }\mathbf{l}$and $\stackrel{\mathbf{→}}{\mathbf{OA}}\mathbf{âŠ\yen }\stackrel{\mathbf{→}}{\mathbf{OC}}$.

If $m∠3=37$, complete:

$m∠4=\underset{¯}{?}$ $m∠5=\underset{¯}{?}$ $m∠6=\underset{¯}{?}$

Give a full twist to a long, narrow strip of paper. Tape the ends together. How many sides does this band have? Cut this band lengthwise down the middle. Write a brief description of what is formed.

Name or state the postulate, property, definition or theorem that justifies the statement.

If $∠AOB$is a right angle, then $\stackrel{↔}{OA}âŠ\yen \stackrel{↔}{OB}$, then $∠Kâ‰\dots ∠M$.

Write something you can conclude from the given information.

Given:$m∠6=m∠4$

Write the biconditional as two conditionals that are converse of each other:

Angles are congruent if and only if their measures are equal.

Name the definition or state the theorem that justifies the statement about the diagram.

If$∠EBC$ is a right angle, then $\stackrel{→}{BE}âŠ\yen \stackrel{↔}{AC}$.