初中数学知识点整?- 百度文库

5ϵжԳƵ

1ԭԳƵĵ

ԭԳʱǵĺ궼ֱΪ෴PxyԭĶԳƵΪP(-x-y)

2xԳƵĵ

xԳʱǵĺ겻䣬껥Ϊ෴PxyxĶԳƵΪP(x-y) 3yԳƵĵ

yԳʱǵĺ껥Ϊ෴겻䣬PxyyĶԳƵΪP(-xy)

ʮ ͼε

1߶εظ

1߶εıȣ

ѡͬһȵλ߶abijȷֱΪmnô˵߶εı

am?дa:b = m:n߶εıָǵij֮ȡ߶εbna:bУaȵǰbȵĺ

2߶Σ

߶У߶εıȵ߶εıȣô߶νɱ߶ΣƱ߶Ρ

abcda:b = c:dôabcdɱ߶Σadbc߶εdabcĵıΪͬ߶Σ2

1 a:b = c:d ?ad?bc

2ab?a:b = b:cô߶b߶acı bcac? ?ad?bc bd a:b = b: c ?b?ac֮ = ֮

?ab?c?d?ac?dc2ʣ????

bd?ba?daͬʱ?c?b?3ʣȵǰ4ϱʣ

acbd??= bdacaca?bc?d??? bdbd35

5ȱʣ

acena?c?e??mb????b?d?f??n?0?? bdfmb?d?f??na3ƽָ

߶ABֳ߶ACBCAC>BCʹACABBCı߶ABƽָC߶ABĻƽָ㣬AC=ƽȡ0.618

ͼC߶ABĻƽָ㣬һ߶2ƽָ㡣

5?1

AB ?0.618AB 2

ACBC?䷽?ȫABAC

2ƽ߷߶γɱ

1ƽֱ߽ߣõĶӦ߶γɱͼl1l2l3

ac? bd

1ƽһߵֱ߽ߣߵӳߣõĶӦ߶

ɱͼڡABCУDEBC

ADAEADAEDE??? BDCEABACBC1涨һֱ߽εߣߵӳߣõĶ

Ӧ߶γɱôֱƽεĵߡ

2ƽһҺֱཻ߽صõεԭε

߶Ӧɱ

3

1εĸ

ӦȣӦ߳ɱνΡ÷šסʾڡζӦߵıȽƱȣϵƱȵ1ȫȣȫƵ 2εĻ

ƽһߵֱߺߣߵӳߣཻɵԭơͼ

36

ѧԱ£DEBCADEסABC εĵȼ۹ϵ

1ԣABCСABCסABC 2ԳԣABCסA?B?C?A?B?C?סABC

3ԣABCסA?B?C?ҡA?B?C?סA??B??C??ABCסA??B??C?? 3ε

1εĶӦȣӦ߳ɱ

2ζӦߵıȡӦߵıӦƽߵıȶƱ 3ܳıȵƱ

4ıȵƱȵƽ

4Ƶж

ж1ǶӦȵơ

ж2߶ӦɱҼнȵơ ж3߶Ӧɱ 5ƶ

1ͬĶεĶӦȣӦ߳ɱôνƶΡƶζӦߵıȽƱȣϵ 2ƶε

ƶεĶӦȣӦ߳ɱ

ƶܳıȡӦԽߵıȶƱ

ƶеĶӦƣƱȵƶεƱ

ƶıȵƱȵƽ 6λͼ

1壺ͼβͼΣÿӦֱ߶ͬһ㣬ôͼνλͼΣλģʱƱȽλƱȡλƷΪͬλƺλơ

ͬλƣλͼεͬ λƣλͼ֮

2ʣÿһӦλͬһֱϣǵλĵľ֮ȶλƱȡ

3λƱ任һͼεõλͼεı任λƱ任λƱ任԰һͼηŴС

37

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