maths! maths! maths!

meilk豆腐貓

2009-07-24 10:47 pm

p. 29
1. In the figure, AOB is a straight line. Which of the following is fasle?
Figure : http://www.flickr.com/photos/29635386@N06/3750951111/
a. [///] AOB=180度 b. x+y=180度 c. x=180度-y d. x=y-180度
[///] : http://www.flickr.com/photos/29635386@N06/3751746870/

2. In the figure, find b.
Figure : http://www.flickr.com/photos/29635386@N06/3751741902/
a. 35度 b. 55度 c. 125度 d. 145度

3. In the figure, AB//CD. Find x.
Figure : http://www.flickr.com/photos/29635386@N06/3751741856/
a. 30度 b. 45度 c.75度 d. 90度

4. In the figure, MBDN is a straight line and AB//CD. Find x.
Figure : http://www.flickr.com/photos/29635386@N06/3750951135/
a. 30 b. 45 c . 75 d. 120
5. In the figure, PQRS is a parallelogram. Which of the following is false?
Figure : http://www.flickr.com/photos/29635386@N06/3751741704/
a. b+c=180度 b. c+d=180度 c. b+d=180度 d. a+d=180度

回答 (1)

Prof. Physics

2009-07-25 12:36 am

✔ 最佳答案

1. Option D is false.

A. AOB is actually a straight line, so angle AOB = 180*

B. x + y = 180* (adj. angles on st. line)

C. Since x + y = 180*, we have x = 180* - y

D. x = 180* - y, not x = y - 180*

2. The answer is C.

a + 35* = 90*

a = 90* - 35* = 55*

a + b = 180* (adj. angles on st. line)

55* + b = 180*

b = 180* - 55* = 125*

3. The answer is B.

Since AB // CD

So, x + 3x = 180* (int. angles, AB // CD)

4x = 180*

x = 180* / 4 = 45*

4. The answer is B.

Since AB // CD

So, angle ABD = angle CDN = (2x - 5)* (corr. angles, AB // CD)

Angle ABD + Angle ABM = 180* (adj. angles on st. line)

(2x - 5)* + (2x + 5)* = 180*

4x* = 180*

x = 45

5. The answer is C.

A. b + c = 180* (alt. angles, PQ // SR)

B. c + d = 180* (alt. angles, PS // QR)

C. b should equal to d, and from the figure, both b and d are obtuse. So, b + d > 180*.

D. Since b = d

And a + b = 180* (adj. angles on st. line)

So, a + d = 180*

參考: Physics king

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