填充題
2.
Calculate \( \displaystyle cos \frac{\pi}{17} \cdot cos \frac{2 \pi}{17} \cdot cos \frac{4 \pi}{17} \cdot cos \frac{8 \pi}{17}=\underline{\frac{1}{16}} \)
[提示]
\( \displaystyle \frac{1}{sin \frac{\pi}{17}}\cdot sin \frac{\pi}{17} \cdot cos \frac{\pi}{17} \cdot cos \frac{2 \pi}{17} \cdot cos \frac{4 \pi}{17} \cdot cos \frac{8 \pi}{17} \)
3.
In the coordinates plane，OABC is a rectangle ， let A(4,3)，\( \overline OC=2 \)，then the coordinates of point B is \( \underline{(2.8,4.6)} \)
[解答]
\( \displaystyle \sqrt{29} \cdot (\frac{4}{5}+\frac{3}{5}i) \cdot (\frac{5}{\sqrt{29}}+\frac{2}{\sqrt{29}}i)=\frac{14}{5}+\frac{23}{5}i \)
10.
Evaluate the integral \( \displaystyle \int^2_0 \frac{2x+4}{x^2+4x+3} dx=\underline{ln5} \)
[提示]
\( \displaystyle \frac{2x+4}{x^2+4x+3}=\frac{1}{x+1}+\frac{1}{x+3} \)
[ 本帖最後由 bugmens 於 2009-7-6 06:55 PM 編輯 ]
