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Complementary and Supplementary Angles
Section 7.2
(continued) (pages 280 and 281)
21. Sample answer: 1) Draw one angle, then draw the other using a side of the first angle;
2) Draw a right angle, then draw the shared side.
23. a. 25°
30°
25. 54°
b. 65°
5
12
27. x = 10; y = 20
29. n = −—
31. B
Triangles
Section 7.3
(pages 286 and 287)
1. Angles: When a triangle has 3 acute angles, it is an acute triangle. When a triangle has 1 obtuse
angle, it is an obtuse triangle. When a triangle has 1 right angle, it is a right triangle. When a
triangle has 3 congruent angles, it is an equiangular triangle.
Sides: When a triangle has no congruent sides, it is a scalene triangle. When a triangle has
2 congruent sides, it is an isosceles triangle. When a triangle has 3 congruent sides, it is an
equilateral triangle.
3. Sample answer:
5. Sample answer:
55°
65°
6 cm
60°
7. equilateral equiangular
6 cm
9. right scalene
11. obtuse scalene
13. acute isosceles
4 cm
15.
60°
20°
17.
100°
2 in.
obtuse scalene triangle
19.
40°
3 in.
21. no; The sum of the angle measures must be 180°.
23. many; You can change the angle formed by the two given sides to create many triangles.
25. no; The sum of any two side lengths must be greater than the remaining length.
A28
Selected Answers
MSCA7PE_Selected Ans.indd A28
4/16/13 2:33:29 PM
27. a. green: 65; purple: 25; red: 45
b. The angles opposite the congruent sides are congruent.
c. An isosceles triangle has at least two angles that are congruent.
29. no; The equation cannot be written as y = kx.
31. B
Angle Measures of Triangles
Extension 7.3
(pages 288 and 289)
1. 91; obtuse scalene triangle
3. 90; right scalene triangle
5. 48; acute isosceles triangle
7. yes
2
3
9. no; 28 —
11. 67.5; acute isosceles triangle
13. 24; obtuse isosceles triangle
15. 35; obtuse scalene triangle
17. a. 72
Selected Answers
b. You can change the distance between the bottoms of the two upright cards; yes; x must be
greater than 60 and less than 90; If x were less than or equal to 60, the two upright cards
would have to be exactly on the edges of the base card or off the base card. It is not possible
to stack cards at these angles. If x were equal to 90, then the two upright cards would be
vertical, which is not possible. The card structure would not be stable. In practice, the limits
on x are probably closer to 70 < x < 80.
Quadrilaterals
Section 7.4
(pages 296 and 297)
1. all of them
3. kite; It is the only type of quadrilateral listed that does not have opposite sides that are
parallel and congruent.
5. trapezoid
7. kite
11. 110
9. rectangle
13. 58°
15.
17.
100°
3 cm
3 cm
75°
4 cm
3 cm
3 cm
100°
19. always
21. never
23. sometimes
Selected Answers
MSCA7PE_Selected Ans.indd A29
A29
4/16/13 2:33:30 PM