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# [M2] limit revision quesions

## limit revision quesions

Thank you very much

Some question I don't why I mixed up the positive and negative signs.

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 風之男 學院師父 發短消息 加為好友 當前在線 2# 大 中 小 發表於 2021-6-12 03:42 PM (第 49 天) 只看該作者 [顯示] [隱藏] As it's a repeated "offense", I urge you to please show your workings and thoughts when asking a math question, no matter how far you get or if it's wrong. Usually you can at least do something by carefully re-reading the question or reviewing what you've learnt. Math is not a spectator sport. Running into dead ends is part of the process, and makes solving a problem eventually even more rewarding. If you see a limit tending to -infty, use a substitution of y=-x for the very first step to make things easier. 46 should be manageable now. 48 is in a form of "sqrt + sqrt" (well, x is just sqrt(x^2), kind of. Beware of signs). You should know what to do. For 50, hopefully when you see sine, you are immediately inspired, at some point, to use "limit as A tends to 0 sinA/A = 1". Now where to apply it is not yet apparent (but still you need to know this technique for diff. by first principles). Here's a well-known enough limit that isn't taught, but I just use it anyway (and state it explicitly when you use it). "limit as A tends to 0 of (1-cosA)/A = 0" As to why this is true, multiply and divide (1+cosA) and see what happens. Solution to 50 in a bit. EDIT: Solution to 50 - https://www.docdroid.net/afWv6mC/limits-2-pdf [ 本帖最後由 風之男 於 2021-6-12 04:22 PM 編輯 ] UID216418 帖子933 精華0 積分115 閱讀權限40 在線時間1569 小時 註冊時間2011-5-4 最後登錄2021-7-31  查看詳細資料 TOP

## 回覆 2# 風之男 的帖子

Thank you very much for your kind assistance.

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