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sin2 x+cos2 x=1
Paritate Perioada Semn Unghi dublusin (−x )=−sin xcos (−x )=−cos xtg (−x )=−tg xctg (−x )=−ctg x
sin ( x+2kπ )=sin xcos (x+2kπ )=cos xtg (x+kπ )=tg xctg ( x+kπ )=ctg x
sin++−−¿¿cos±−+¿¿tg±+−¿¿ctg±+−¿¿
cos2a=cos2a−sin2a=1−2sin2a¿2cos2a−1sin 2a=2sin a∙cos a
tg a= 2 tg a
1−tg2aReducerea la primul
cadranFormule de baza Transformarea produselor in sume
x II →I π−xx III→ I x−πx IV → II 2π−x
cos (a−b )=cos a ∙cos b+sina ∙ sinbcos (a+b )=cosa ∙cosb−sina ∙ sinbsin (a−b )=sina ∙cosb−sinb ∙cosasin (a+b )=sina ∙cos b+sinb ∙cosa
tg (a−b )= tg a−tgb1+tg a∙ tg b
tg (a+b )= tg a+tg b1−tg a∙ tg b
sin x ∙ sin y=cos ( x− y )−cos (x+ y )
2
cos x ∙cos y=cos ( x+ y )+cos (x− y )
2
sin x ∙cos y=sin ( x− y )−sin(x+ y )
2
Alte formule importante Transformarea sumelor in produse
sinx2=± √1−cosx
2
cosx2=± √1+cosx
2
tgx2= sinx1+cosx
ctg 2x=1−t g2 x
2tgx
sin x=a→ xk=¿cos x=¿b→xk=± arccosb+2kπ ¿tg x=¿c→ xk=arctg c+kπ ¿ctg x=¿d→xk=arcctgd+kπ ¿
arctg a±arctgb=arctg (a+b )1−ab
arctg a−arctgb=arctg (a−b )1+ab
12∙(1+t g2 x2 )=2(tg x2 ) '
sin2 x=1−cos2 x2
cos2 x=1+cos2 x2
sina+sinb=2sin a+b2∙cos
a−b2
sina−sinb=2sin a−b2∙cos
a+b2
cos a+cosb=2cos a+b2∙cos
a−b2
cos a−cos b=−2sin a+b2∙ sin
a−b2
tg a+tg b=sin(a+b)cos a∙cos b
tg a−tg b=sin(a−b)cosa ∙cosb
Treceri importante Trecerea simpla
sina=¿2tg
a2
1+tg2a2
¿
cos a=¿1−tg2 a
2
1+tg2a2
¿
sin( π2−x)=cos x
cos ( π2−x )=sin x
tg( π2−x)=ctg x
ctg( π2−x)=tg x
tg a=¿2 tg
a2
1−tg2a2
¿1+tg2 a
2= 1
cos2a2
=¿
¿( tg a2 )'
∙2