𡿽⣺1ݰС˳Ϊ6788910 ԸݵλΪ8Ϊ8 2ݵƽ=
=8
Ըݵķ=[682+782+882+882+982+1082]= ʴΪ88
˷һиǵƽIJƽƽݵķ㹫ʽǣs2=x1x2+x2x2++xnx2]
198֣ͼEFǾABCDBCϵ㣬AF=DE 1DAFFAB=57AFB= 37.5 㣻 2֤BE=CF
1DAFƽߵAFBɣ 2ֻҪ֤ABFաDCEɽ⣻ 𡿽⣺1ıABCDǾΣ BAD=90㣬ADBC ߡDAFFAB=57 DAF=
90=37.5㣬
AFB=DAF=37.5㣬 ʴΪ37.5
2ıABCDǾΣ B=C=90㣬AB=CD
13ҳ19ҳ
AF=DE
RtABFRtDCE BF=EC BE=CF
εʡȫεжʵ֪ʶĹؼѧ֪ʶ⣬пͣ
209֣֪y+4xx=6ʱy=8 1yx֮ĺϵʽ
2ֱϵͼлͼ 3ֱд4y0ʱԱxȡֵΧ
1Ķy+4=kxk0Ȼ֪ݴмkֵɵý⣻
2Ľ㣬Ȼ㷨ͼɣ 3ͼɵýۣ
𡿽⣺1y+4x y+4=kxk0 ߵx=6ʱy=8
14ҳ19ҳ
8+4=6k k=2 y+4=2x
ϵʽΪy=2x4
2x=0ʱy=4 y=0ʱ2x4=0x=2
ԣͼ㣨0420 ͼͼ
3ͼã4y0ʱԱxȡֵΧǣ0x2
˴ϵһκʽһκͼĶʽǽĹؼ
219֣֪ͼڡABCУB=45㣬C=60㣬AB=31A= 75 㣻 2ABCľ룻
3BCijøűʾ
1ڽǺͶ㼴ɣ
15ҳ19ҳ
2ҵĶAD
3еĶCD㼴ɣ 𡿽⣺1A=180㩁B+C=75㣬 ʴΪ75 2ADBCD
RtABDУAD=ABsinB=3 ABCľΪ3
3RtABDУBD=ABcosB=3 RtACDУCD=BC=BD+CD=3+
=
ǽֱΣǺĸǽĹؼ
2210֣ͼƽֱϵУֱl1y=x+6ֱxᡢyύڵBCֱl2y=xڵA 1A꣮
2D߶OAϵĵ㣬ҡCODΪ12ֱCDĺʽ 3ڣ2£PCDϵĵ㣬ƽǷڵQʹOCPQΪıΣڣֱдPꣻڣ˵ɣ
1ֱ߽ʽA꼴ɣ
16ҳ19ҳ