Then a right angle is an angle of how many degrees? If an angle stand upon less than 90°, what kind of an angle is it? If an angle stand upon more than 90°, what kind of an angle is it? Can an angle have as many degrees as a hundred and eighty? LESSON THIRTY-FIFTH. REVIEW. Read nine arcs whose ends are marked. (DIAGRAM 26.) Read three arcs each of which is one-fourth of a circumference. Read two arcs each of which is one-half of a circumference. Why is _e g_ an arc? What is an arc? How many degrees in the arc _f h_? In _e h_? If the arc _f h_ were divided into three equal parts, how many degrees would there be in each? How many degrees in a circumference? In a semi-circumference? How many more degrees in a large circumference than in a small one? If the arc _i f_ is 40°, what is the size of the angle _f o i_? If the angle _f o g_ is an angle of 130°, what is the size of the arc _f i h g_? How many degrees in each of the adjacent angles _f o h_, _h o e_? When two adjacent angles are equal to each other, what is each called? How many degrees in a right angle? [Illustration: Diagram 26.] LESSON THIRTY-SIXTH. PARTS OF THE CIRCLE. The part of the circle bounded by the chord _a b_ and the arc _a b_ is called a segment. Read three segments, each less than half a circle, thus,—the segment bounded by the chord _a d_ and the arc _a b d_. _A segment is a part of a circle bounded by an arc and a chord._ Read two segments that are each half a circle. What is the chord called? What is the arc called? A segment bounded by a diameter and a semi-circumference is a “_semicircle_.” _A semicircle is half a circle._ Read four segments each larger than a semicircle. The part of the circle between the two radii _o f_, _o i_, and the arc _f i_, is called a “_sector_.” Read four sectors each less than one-fourth of a circle.[2] Footnote 2: Thus, a sector bounded by the two radii _o g_, _o h_, and the arc _g h_. _A sector is a part of a circle bounded by two radii and an arc._ What part of the whole circle is the sector _f o h_? It is called a “_quadrant_.” _A quadrant is a sector which is one-fourth of a circle._ Read a sector which is greater than a quadrant. If the chord _e f_ be regarded a diameter, what do you call the semicircle below it? If it be regarded as two radii, what is the semicircle called? Then a semicircle is both a segment and a sector. LESSON THIRTY-SEVENTH. REVIEW. Name ten segments. (DIAGRAM 26.) What is a segment? Of the segments named, which are less than a semicircle? Which are greater? Which two are semicircles? Which two are on the chord _a f_? Name nine sectors.