再來兩個不定積分

2008-08-02 3:31 am
Find the integrals of

1/[ x^(1/2) + x^(1/3) ]

Square root of { sqrt(2) + sin[sqrt(x)] + cos[sqrt(x)]}

回答 (4)

2008-08-06 11:57 am
✔ 最佳答案

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參考資料:
修改自http://i117.photobucket.com/albums/o61/billy_hywung/Aug08/Crazyint1.jpg及http://i187.photobucket.com/albums/x22/cshung/7008080102888.png + my maths knowledge
2008-08-02 10:27 pm
Q2 : 經開方後出現絕對值

sqrt[ 1 + sqrt(丌/4 + u)]
= | sin(丌/8 + y/2) + cos(丌/8 + y/2) |

2008-08-02 14:30:37 補充:


sqrt[ 1 + sin(丌/4 + y)]先岩

= sqrt[ sin^2 u + cos^2 u + 2sin(u)cos(u) ]
= sqrt( sinu + cosu )^2
= | sinu + cosu |

u係咩任人定

2008-08-03 10:44:19 補充:
那咩時候係咩case?我唔識這樣....
有沒有什麼不等式
2008-08-02 8:22 pm
http://i187.photobucket.com/albums/x22/cshung/7008080102888.png

(For Q2)

There is a bug in the proof, can you find it? :p

2008-08-02 18:48:37 補充:
既然你搵到了咁即係你識做啦
分番晒case就得,太煩唔做了。

2008-08-05 20:12:39 補充:
Let S = sin(y/2 + pi/8)
C = cos(y/2 + pi/8)

Case 1: S is positive, C is positive, S >= C => |S - C| = S - C
Case 2: S is positive, C is positive, S < C => |S - C| = C - S

Case 3: S is positive, C is negative => |S - C| = S + C
Case 4: S is negative, C is positive => |S - C| = -S - C

2008-08-05 20:12:46 補充:
Case 5: S is negative, C is negative, S >= C => |S - C| = S - C
Case 6: S is negative, C is negative, S < C => |S - C| = C - S

Notice, Case 1 = Case 5, Case 2 = Case 6, there are really just 4 cases.
You can represent the solution with all these cases.


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