Language For Exercises 39–42, use the chart below. Decide whether the description of each letter is a good definition. If not, provide a counterexample by giving another letter that could fit the definition.

Image Long Description

39. The letter D is formed by pointing straight up with the finger beside the thumb and folding the other fingers and the thumb so that they all touch.
40. The letter K is formed by making a V with the two fingers beside the thumb.
41. You have formed the letter I if and only if the smallest finger is sticking up and the other fingers are folded into the palm of your hand with your thumb folded over them and your hand is held still.
42. You form the letter B by holding all four fingers tightly together and pointing them straight up while your thumb is folded into the palm of your hand.

Reading Math Let statements p, q, r, and s be as follows:

• p : ∠ A p colon angle eh  and ∠ B angle b  are a linear pair.
• q : ∠ A q colon angle eh  and ∠ B angle b  are supplementary angles.
• r : ∠ A r colon angle eh  and ∠ B angle b  are adjacent angles.
• s : ∠ A s colon angle eh  and ∠ B angle b  are adjacent and supplementary angles.

Substitute for p, q, r, and s, and write each statement the way you would read it.

43. p → q p rightwards arrow q
44. p → r p rightwards arrow r
45. p → s p rightwards arrow s
46. p ↔ s p left right arrow s

C Challenge

47. Writing Use the figures to write a good definition of a line in spherical geometry.

    

    

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