1) Which of the following pairs of points lies in the same quadrant?
A (-2,3) , (5,8)
B (8,2) , (4,3)
C (9,-1) , (-2,-3)
D (4,2) , (5,-1)
2) Find the area of OAB in the figure.
***P.S. A (-1,3) , B (-3,-2)
3) Find the area of the quadrilateral ABCD in the figure.
***P.S. A (-2,3) , B (-3,-1) , C (-2,-2) , D (2,2)
請問這三條數學題怎樣做
2007-08-19 7:38 pm
回答 (1)
2007-08-19 10:34 pm
✔ 最佳答案
1) B2)
Draw a rectangle enclosed the triangle OAB
the sides of the rectangle must be horizontal and vertical
width is 3 and height is 5, area is 15
Area OAB = 15 - |[(XA-XB)(YA-YB)]/2|-|(XA*YA)/2|-|(XB*YB)/2|
= 15 - 5 - 1.5- 3
= 5.5
3)
Draw a rectangle enclosed the quadrilateral ABCD
the sides of the rectangle must be horizontal and vertical
width is 5 and height is 5, area is 25
Area of quadrilateral ABCD = half of the rectangle
= 25 / 2 = 12.5
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