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sin
2
α
+
cos
2
α
=
1
,
sin
α
cos
α
=
tan
α
,
sin
α
⋅
csc
α
=
1
{\displaystyle \sin ^{2}\alpha +\cos ^{2}\alpha =1,\quad {\frac {\sin \alpha }{\cos \alpha }}=\tan \alpha ,\quad \sin \alpha \cdot \csc \alpha =1}
,
sec
2
α
−
tan
2
α
=
1
,
cos
α
⋅
sec
α
=
1
{\displaystyle \sec ^{2}\alpha -\tan ^{2}\alpha =1,\qquad \cos \alpha \cdot \sec \alpha =1}
,
csc
2
α
−
cot
2
α
=
1
,
cos
α
sin
α
=
cot
α
,
tan
α
⋅
cot
α
=
1
{\displaystyle \csc ^{2}\alpha -\cot ^{2}\alpha =1,\quad {\frac {\cos \alpha }{\sin \alpha }}=\cot \alpha ,\quad \tan \alpha \cdot \cot \alpha =1}
Međusobno izražavanje funkcija
sin
α
=
1
−
cos
2
α
=
tan
α
1
+
tan
2
α
,
{\displaystyle \sin \alpha ={\sqrt {1-\cos ^{2}\alpha }}={\frac {\tan \alpha }{\sqrt {1+\tan ^{2}\alpha }}},}
cos
α
=
1
−
sin
2
α
=
1
1
+
tan
2
α
,
{\displaystyle \cos \alpha ={\sqrt {1-\sin ^{2}\alpha }}={\frac {1}{\sqrt {1+\tan ^{2}\alpha }}},}
tan
α
=
sin
α
1
−
sin
2
α
=
1
cot
α
,
{\displaystyle \tan \alpha ={\frac {\sin \alpha }{\sqrt {1-\sin ^{2}\alpha }}}={\frac {1}{\cot \alpha }},}
cot
α
=
1
−
sin
2
α
sin
α
=
1
tan
α
.
{\displaystyle \cot \alpha ={\frac {\sqrt {1-\sin ^{2}\alpha }}{\sin \alpha }}={\frac {1}{\tan \alpha }}.}
Funkcije zbira i razlike
sin
(
α
±
β
)
=
sin
α
cos
β
±
cos
α
sin
β
,
{\displaystyle \sin(\alpha \pm \beta )=\sin \alpha \cos \beta \pm \cos \alpha \sin \beta ,\,}
cos
(
α
±
β
)
=
cos
α
cos
β
∓
sin
α
sin
β
,
{\displaystyle \cos(\alpha \pm \beta )=\cos \alpha \cos \beta \mp \sin \alpha \sin \beta ,}
tan
(
α
±
β
)
=
tan
α
±
tan
β
1
∓
tan
α
tan
β
,
cot
(
α
±
β
)
=
cot
α
cot
β
∓
1
cot
β
±
cot
α
.
{\displaystyle \tan(\alpha \pm \beta )={\frac {\tan \alpha \pm \tan \beta }{1\mp \tan \alpha \tan \beta }},\quad \cot(\alpha \pm \beta )={\frac {\cot \alpha \cot \beta \mp 1}{\cot \beta \pm \cot \alpha }}.}
tan
2
α
=
2
tan
α
1
−
tan
2
α
,
tan
3
α
=
3
tan
α
−
tan
3
α
1
−
3
tan
2
α
,
{\displaystyle \tan 2\alpha ={\frac {2\tan \alpha }{1-\tan ^{2}\alpha }},\tan 3\alpha ={\frac {3\tan \alpha -\tan ^{3}\alpha }{1-3\tan ^{2}\alpha }},}
sin
2
α
=
2
sin
α
cos
α
,
sin
3
α
=
3
sin
α
−
4
sin
3
α
,
{\displaystyle \sin 2\alpha =2\sin \alpha \cos \alpha ,\quad \sin 3\alpha =3\sin \alpha -4\sin ^{3}\alpha ,}
cos
2
α
=
cos
2
α
−
sin
2
α
,
cos
3
α
=
4
cos
3
α
−
3
cos
α
,
{\displaystyle \cos 2\alpha =\cos ^{2}\alpha -\sin ^{2}\alpha ,\quad \cos 3\alpha =4\cos ^{3}\alpha -3\cos \alpha ,}
tan
2
α
=
2
tan
α
1
−
tan
2
α
,
tan
3
α
=
3
tan
α
−
tan
3
α
1
−
3
tan
2
α
,
{\displaystyle \tan 2\alpha ={\frac {2\tan \alpha }{1-\tan ^{2}\alpha }},\quad \tan 3\alpha ={\frac {3\tan \alpha -\tan ^{3}\alpha }{1-3\tan ^{2}\alpha }},}
cot
2
α
=
cot
2
α
−
1
2
cot
α
,
cot
3
α
=
cot
3
α
−
3
cot
α
3
cot
2
α
−
1
,
{\displaystyle \cot 2\alpha ={\frac {\cot ^{2}\alpha -1}{2\cot \alpha }},\quad \cot 3\alpha ={\frac {\cot ^{3}\alpha -3\cot \alpha }{3\cot ^{2}\alpha -1}},}
tan
4
α
=
4
tan
α
−
4
tan
3
α
1
−
6
tan
2
α
+
tan
4
α
,
cot
4
α
=
cot
4
α
−
6
cot
2
α
+
1
4
cot
3
α
−
4
cot
α
.
{\displaystyle \tan 4\alpha ={\frac {4\tan \alpha -4\tan ^{3}\alpha }{1-6\tan ^{2}\alpha +\tan ^{4}\alpha }},\quad \cot 4\alpha ={\frac {\cot ^{4}\alpha -6\cot ^{2}\alpha +1}{4\cot ^{3}\alpha -4\cot \alpha }}.}
Na osnovu ovih formula možemo odrediti predznak trigonometrijskih funkcija po kvadrantima
Kvadrant
0°- 90°
90°- 180°
180°- 270°
270°- 360°
sinus
+
+
-
-
kosinus
+
-
-
+
tangens
+
-
+
-
kotangens
+
-
+
-
Zbir i razlika trigonometrijskih funkcija
sin
α
+
sin
β
=
2
sin
α
+
β
2
cos
α
−
β
2
,
{\displaystyle \sin \alpha +\sin \beta =2\sin {\frac {\alpha +\beta }{2}}\cos {\frac {\alpha -\beta }{2}},}
sin
α
−
sin
β
=
2
cos
α
+
β
2
sin
α
−
β
2
,
{\displaystyle \sin \alpha -\sin \beta =2\cos {\frac {\alpha +\beta }{2}}\sin {\frac {\alpha -\beta }{2}},}
cos
α
+
cos
β
=
2
cos
α
+
β
2
cos
α
−
β
2
,
{\displaystyle \cos \alpha +\cos \beta =2\cos {\frac {\alpha +\beta }{2}}\cos {\frac {\alpha -\beta }{2}},}
cos
α
−
cos
β
=
−
2
sin
α
+
β
2
sin
α
−
β
2
,
{\displaystyle \cos \alpha -\cos \beta =-2\sin {\frac {\alpha +\beta }{2}}\sin {\frac {\alpha -\beta }{2}},}
tan
α
±
tan
β
=
sin
(
α
±
β
)
cos
α
cos
β
,
cot
α
±
cot
β
=
±
sin
(
α
±
β
)
sin
α
sin
β
,
{\displaystyle \tan \alpha \pm \tan \beta ={\frac {\sin(\alpha \pm \beta )}{\cos \alpha \cos \beta }},\quad \cot \alpha \pm \cot \beta =\pm {\frac {\sin(\alpha \pm \beta )}{\sin \alpha \sin \beta }},}
tan
α
+
cot
β
=
cos
(
α
−
β
)
cos
α
sin
β
,
cot
α
−
tan
β
=
c
o
s
(
α
+
β
)
sin
α
cos
β
.
{\displaystyle \tan \alpha +\cot \beta ={\frac {\cos(\alpha -\beta )}{\cos \alpha \sin \beta }},\quad \cot \alpha -\tan \beta ={\frac {cos(\alpha +\beta )}{\sin \alpha \cos \beta }}.}
Proizvod funkcija
sin
α
sin
β
=
1
2
[
cos
(
α
−
β
)
−
cos
(
α
+
β
)
]
,
{\displaystyle \sin \alpha \sin \beta ={\frac {1}{2}}[\cos(\alpha -\beta )-\cos(\alpha +\beta )],}
cos
α
cos
β
=
1
2
[
cos
(
α
−
β
)
+
c
o
s
(
α
+
β
)
]
,
{\displaystyle \cos \alpha \cos \beta ={\frac {1}{2}}[\cos(\alpha -\beta )+cos(\alpha +\beta )],}
sin
α
cos
β
=
1
2
[
sin
(
α
+
β
)
+
sin
(
α
−
β
)
]
.
{\displaystyle \sin \alpha \cos \beta ={\frac {1}{2}}[\sin(\alpha +\beta )+\sin(\alpha -\beta )].}
Funkcije polovine ugla
sin
α
2
=
1
−
cos
α
2
,
cos
α
2
=
1
+
cos
α
2
,
{\displaystyle \sin {\frac {\alpha }{2}}={\sqrt {\frac {1-\cos \alpha }{2}}},\quad \cos {\frac {\alpha }{2}}={\sqrt {\frac {1+\cos \alpha }{2}}},}
tan
α
2
=
1
−
cos
α
1
+
cos
α
=
1
−
cos
α
sin
α
=
sin
α
1
+
cos
α
,
{\displaystyle \tan {\frac {\alpha }{2}}={\sqrt {\frac {1-\cos \alpha }{1+\cos \alpha }}}={\frac {1-\cos \alpha }{\sin \alpha }}={\frac {\sin \alpha }{1+\cos \alpha }},}
cot
α
2
=
1
+
cos
α
1
−
cos
α
=
1
+
cos
α
sin
α
=
sin
α
1
−
cos
α
.
{\displaystyle \cot {\frac {\alpha }{2}}={\sqrt {\frac {1+\cos \alpha }{1-\cos \alpha }}}={\frac {1+\cos \alpha }{\sin \alpha }}={\frac {\sin \alpha }{1-\cos \alpha }}.}
Stepenovanje funkcija
sin
2
α
=
1
2
(
1
−
cos
2
α
)
,
cos
2
α
=
1
2
(
1
+
cos
2
α
)
,
{\displaystyle \sin ^{2}\alpha ={\frac {1}{2}}(1-\cos 2\alpha ),\quad \cos ^{2}\alpha ={\frac {1}{2}}(1+\cos 2\alpha ),}
sin
3
α
=
1
4
(
3
sin
α
−
sin
3
α
)
,
cos
3
α
=
1
4
(
cos
3
α
+
3
cos
α
)
,
{\displaystyle \sin ^{3}\alpha ={\frac {1}{4}}(3\sin \alpha -\sin 3\alpha ),\quad \cos ^{3}\alpha ={\frac {1}{4}}(\cos 3\alpha +3\cos \alpha ),}
sin
4
α
=
1
8
(
cos
4
α
−
4
cos
2
α
+
3
)
,
cos
4
α
=
1
8
(
cos
4
α
+
4
cos
2
α
+
3
)
.
{\displaystyle \sin ^{4}\alpha ={\frac {1}{8}}(\cos 4\alpha -4\cos 2\alpha +3),\quad \cos ^{4}\alpha ={\frac {1}{8}}(\cos 4\alpha +4\cos 2\alpha +3).}