formule utile clasa a viii a
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FORMULE DE CALCUL PRESCURTAT
(a+b)2=a2+2ab+b2 ; (a-b)2=a2-2ab+b2 ; a2-b2=(a+b)(a-b) ; (a+b+c)2=a2+b2+c2+2ab+2ac+2bc ;
(a+b)3=a3+3a2 b+3ab2+b3 ; (a-b)3=a3-3a2 b+3ab2-b3 ;
a3+b3=(a+b)(a2-ab+b2) ; a3-b3=(a-b)(a2+ab+b2) ;
PROPRIETATILE PUTERILOR
an∙am=an+m ; an:am=an -m ; (an)m=an∙m ; (a∙b)n=an∙bn ; (a:b)n=an:bn ; a0=1 ; 0n=0 ; 1n=1
PROPRIETATILE RADICALILOR
ba ba ⋅=⋅ ; b/a b/a = ; xx2= ; ( ) yy
2
= ; a≥0 ; b>0 ; y≥0 ; exemple:
23292918 =⋅=⋅= ; 7532532535 =⋅=⋅= ; ( ) 333 2
=−=− ; ( ) 662
=
MODULUL!e"#n#$#e : %&%=& 'aca &≥0 # %&%= -& 'aca &0 ;
*,p#e$a$# : %&%≥0 ; %a∙b%=%a%∙%b% ; %a+b%%a%+%b% ;
xemple : %-5%= -(-5)=5 ; %7%=7 ; %-2%= -(-2)=2 ; %+.%=. ;
FUNCTIA LINIARA f :R R , f(x)=ax+b
*(xy)
∈" 'aca # nma# 'aca "(x)=y ;
(xy)∈
" ,x 'aca "(x)=y # y=0 ;
4(xy)∈" ,y 'aca "(x)=y # x=0 ;
!aca " # n$ ',a "nc$## a$nc# (xy)∈"
'aca "(x)=(x)=y ;
(-b/a 0) # 4(0 b)
MULTIMI DE NUMERE
l$#mea nmeel, na$ale n,$a$a c N : 0123.89
l$#mea nmeel, #n$e# n,$a$a c Z : -9 8 -.-3-2-10123.8+9
l$#mea nmeel, a$#,nale n,$a$a c Q: exemple -3/. ;5/2 ;-12/. ;023 ;-5(2.) ;.20(576) ;
l$#mea nmeel, eale n,$a$a c R ; exemple : -3/. ;5/2 ;-1/. ; 6;57 − ; -5(2.) ;
.20(576) ; 02020020002008 ;-523233233323333238 ;
#ce nma na$al e$e nma #n$e : N⊂Z
#ce nma #n$e e$e nma a$#,nal : Z⊂Q
#ce nma a$#,nal e$e nma eal : Q⊂R
em ma$,aele ela$## 'e #ncl<#ne #n$e ace$e ml$#m# : N⊂Z⊂Q⊂R
meele eale cae n n$ nmee a$#,nale e nmec nmee #a$#,nale
FIGURI PLANE REMARCABILE
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4?=2
(#n?4
2
!4? ⋅⋅=
⋅ 4?!=
( )2
4-?!4 ⋅+ 4?!= ?!∙
*4?= 4+4?+? *4?!= 4+4?+?!+! *4?!= 2∙(4+4?)
4?!= 4∙4? 4?!=2
4!? ⋅
?2=42+4?2
*4?!= 2∙(4+4?) *4?!= .∙4
p,l#,ane ela$e : l=la$a p,l#,nl# ; a=ap,$ema p,l#,nl# ; =a#a ; *=pe#me$l ;
*=3∙l *=.∙l *=6∙l
6
3la;
.
3l
2
== 2
la;l 2==
2
3la;
2
3l3
2
==
l=@ 3 l=@ 2 l=@
2
@ 3
2
3lA == '=l 2 =2@
TRIUNGHIUL DREPTUNGHICBe,ema ca$e$e#: b2=a∙n ; c2=a∙m
2
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Be,ema #nal$#m##: A2=m∙n ;a
c bA
⋅=
Be,ema l# *#$a,a: a2=b2+c2 ; c2=A2+m2 # b2=A2+n2
#a $ 'ep$nA#c:2Aa
2c b ⋅=⋅=
FUNCTII TRIGONOMETRICE
"nc$#a 30C 60C .5C "nc$#a 30C 60C .5C
#n
2
1
2
3
2
2 $
3
3 3 1
c,
2
3
2
1
2
2 c$
3 3
3 1
#n xC=?
4
#
,c= c, xC=
?
4?
#
ac= $ xC=
4?
4
ac
,c= c$ xC=
4
4?
,c
ac=
NOTATII UTILIZATE IN GEOMETRIA CORPURILOR REGULATE
l Da#a la$eala ; $ Da#a $,$ala ; E- ,lml ; a p-ap,$ema p#am#'e# ; a$ -ap,$ema $ncA#l#
b-a#a ba<e# m#c# ; 4-a#a ba<e# ma# ; * b-pe#me$l ba<e# m#c# ; *4-pe#me$l ba<e# ma# ;
A-#nal$#mea c,pl# ; m-mcA#a la$eala ; a b-ap,$ema ba<e# m#c# ; a4-ap,$ema ba<e# ma# ;
l-la$a ba<e# m#c# ; F-la$a ba<e# ma# ; -enea$,aea (la c#l#n' c,n $ncA# 'e c,n) ;
-a<a ba<e# m#c# ; @-a<a ba<e# ma#
PRISMA , PIRAMIDA , TRUNCHIUL DE PIRAMIDA
l=*4∙m l=2
a* p4 ⋅ l=
( )2
a** $+ 4 b ⋅+
$=l+2∙4 $=l+4 $=l+ b+4
E=4∙A E=3
A4 ⋅
E= ( )
3
A4 b4 b
⋅++⋅
G,mlele n$ alab#le pen$ ,#cae p#ma ela$a p#am#'a ela$a a $ncA# 'e
p#am#'a ela$a (,#cae a "# nmal 'e la$# ale ba<e#)
CILINDRUL ,CONUL ,TRUNCHIUL DE CON
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= @2π l= @π l= ( )+ @ +π
$= ( )@ @ 2 +π $= ( )@ @ +π $=
( ) 22 + @ + @ π+π++π
E= A@ 2π E=3
A@ 2π
E= ( )
3
+ @ + @ A 22
⋅++π
SFERA ,CALOTA SFERICA ,PARALELIPIPEDUL DREPTUNGHIC
= 2@ .π c= @A2π $= ( ) bcacab2 ++⋅
E=3
@ . 3π
@ 2= 2+(@-A)2 E= a∙b∙c
2222c ba' ++=
TRIUNGHIURI ASEMENEA ,TEOREMA LUI THALES
e<l$a: =*
4?
7*
?
7=
4== e<l$a:
=
?
7
4=
CERCUL
!aca m ,x:4 =∠ a$nc# :
Fc= @ 2π ; F4=,
,
180
@xπ
c= 2@ π ; 4=
,
,2
360
x@ π
.