Math problem(急)

用戶25266

2009-09-26 5:35 pm

an isosceles trianlge has its base along the x-axis with one base
vertex at the origin and its vertex in the first quadrant on the graph
of y=6 -x^2. write the area of the triangle as a function of the length
of the base.

(show all the works)
attach with graph if you can

更新1:

The height corresponds to the value y when x = B/2 i dont understand what is that come from?

回答 (1)

用戶9112

2009-09-26 6:24 pm

✔ 最佳答案

圖片參考：http://img143.imageshack.us/img143/6207/triangle.png

Let the base length be B
The height corresponds to the value y when x = B/2
Height = 6 - (B/2)^2 = 6 - B^2/4
Area of triangle = (1/2) Base x Height
= (1/2)(B)(6 - B^2/4)
Area = 3B - B^3/8

2009-09-27 09:20:24 補充：
The co-ordinates of the 2 base vertices are (0,0) and (B,0). Since the triangle is isosceles, the dotted line in the diagram will lead to the mid point (B/2,0) between these 2 vertices. The top vertex is on the graph of 6 - x^2/2. It's x-ordinate is B/2, the y-ordinate is 6 - (B/2)^2/2

2009-09-27 09:21:46 補充：
The y-ordinate of the base is 0, so the height is 6 - (B/2)^2/2

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