They do what they do.
How many pairs of vertical angles are formed by five distinct lines that have a common point of intersection? p. 64
A pair of vertical angles is formed by two lines. You have five lines to choose those two lines from. You have five ways to choose the first line and four ways to choose the second line. But order doesn't matter, so 10 pairs.
Almost, Daniel. You forgot, though that a pair of lines forms TWO pairs of vertical angles.
oh!That's my problem --- I got Daniel's answer --- wasn't thinking about the fact that a pair of vertical lines forms TWO PAIRS of angles!Thank you!
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A pair of vertical angles is formed by two lines.
ReplyDeleteYou have five lines to choose those two lines from. You have five ways to choose the first line and four ways to choose the second line. But order doesn't matter, so 10 pairs.
Almost, Daniel. You forgot, though that a pair of lines forms TWO pairs of vertical angles.
ReplyDeleteoh!
ReplyDeleteThat's my problem --- I got Daniel's answer --- wasn't thinking about the fact that a pair of vertical lines forms TWO PAIRS of angles!
Thank you!