Area of triangle

👨🏻‍🏫 學術台數學

[匿名]

2009-06-19 12:58 am

For the curve y = 2 cos 2x, find the area of triangle bound by the x - axis,
the points on the curve when x = 45 degree, when x = 90 degree and when x = 135 degree in terms of k where 2k is the amplitude of the curve.

更新1:

The question above is as what is stated in the test paper. k should not be 1, if k = 1 then the answer will not be in terms of k. But you are allowed to assume k = 1 to get answer.

更新2:

Note : Answer does not involve pi.

更新3:

Following are the selections: A. k/4, B. k/2, C. k and D. 2k

回答 (2)

STEVIE-G™

2009-06-19 8:03 am

✔ 最佳答案

the amplitude of the curve is 2
then 2k=2
k=1?

2009-06-18 19:09:20 補充：
O....that's funny

2009-06-19 00:03:58 補充：
Firstly , it's better that you sketch the graph of y=2cos2x
The points indicated are (π/4,0) , (π/2,-2) and (3π/4,0)
the area of triangle bound by the x - axis and the three points on the curve
=(3π/4-π/4)(k)/2
=πk/4
~k
Ans: C

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用戶9112

2009-06-19 5:30 am

State the answer from the text book to think backward what the question means.

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