Maths Problem

圖片參考：http://imgcld.yimg.com/8/n/HA00100646/o/701209020027813873365320.jpg


圖片參考：http://imgcld.yimg.com/8/n/HA00100646/o/701209020027813873365321.jpg

Hope I can help you.

2012-09-02 14:24:16 補充：
∠BAC+∠ACB+∠ABC=180°(proved above)
Assume ∠BAC=180°,
the above formula becomes ∠ACB+∠ABC=0°
Assume another angle, say ∠ACB=0°, ∠ABC=0°.
However, interior angles must be >0.
Assume ∠ACB is a positive number, then ∠ABC is negative.
However, angles cannot be negative.
So, it cannot exceed 180°.

2012-09-08 15:09:40 補充：
My personal comment:
Knowledge Plus,
I agree that your method can illustrate and explain why the angle sum of a triangle is 180.
However, in mathematics, your illustration is not a proper proof of this theorem. It is just a way to discover a new theorem.

The size of any interior angle triangle cannot exceed is :

D. 180

2012-09-02 13:26:41 補充：
If you want to know that why the answer should be 180 , you can make a little experiment !
First of all , you need to draw a triangle .
And then , cut down the angles of the triangle with a pair of scissors .
After that , put the angles together .
Finally , you can know that they make a

2012-09-02 13:27:06 補充：
Straight line which is equal to 180

2012-09-02 13:27:54 補充：
I hope this way can be useful to you to understand it !

Knowledge Plus