Trigonometrie clasa a IX-a
Trigonometrie clasa a IX-a
Trigonometrie clasa a IX-a
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x<br />
2 x<br />
2tg<br />
1-tg<br />
2<br />
2 2t 2 1−<br />
t x<br />
sin x = = cosx = = unde t = tg<br />
2 2<br />
2 x 1 2 x<br />
1+ tg<br />
+ t<br />
1+<br />
tg<br />
1+<br />
t<br />
2<br />
2 2<br />
x<br />
2 x<br />
2tg<br />
1-tg<br />
2<br />
2 2t<br />
2 1−<br />
t<br />
tgx = = ctgx= =<br />
2<br />
2 x 1 x<br />
1-tg<br />
− t<br />
2tg<br />
2t<br />
2 2<br />
Formule pentru trasformarea sumelor în produse<br />
x+ y x− y x− y x+<br />
y<br />
sin x+ sin y = 2sin cos sin x− sin y = 2sin cos<br />
2 2 2 2<br />
x+ y x− y x+ y x−<br />
y<br />
cos x+ cos y = 2cos cos cos x− cos y =−2sin sin<br />
2 2 2 2<br />
⎛π<br />
⎞ ⎛ π ⎞<br />
sin x+ cos x= sin x+ sin ⎜ − x⎟= 2 cos⎜x−<br />
⎟<br />
⎝ 2 ⎠ ⎝ 4⎠<br />
Formule pentru trasformarea produselor în sume<br />
1<br />
sin x⋅ cos y = ⎡sin ( ) sin ( )<br />
2<br />
⎣ x+ y + x−<br />
y ⎤⎦<br />
1<br />
cos x⋅ cos y = ⎡cos( x y) cos ( x y)<br />
2<br />
⎣ − + + ⎤⎦<br />
1<br />
sin x⋅ sin y = ⎡cos( x− y) − cos ( x+<br />
y)<br />
⎤<br />
2<br />
⎣<br />
⎦<br />
Ecuatii trigonometrice fundamentale:<br />
π<br />
sin x=−1⇒ x=− + 2kπ<br />
2<br />
sin x= 0 ⇒ x=<br />
kπ<br />
π<br />
sin x= 1⇒ x= + 2kπ<br />
2<br />
cos x=−1⇒ x= π + 2kπ<br />
π<br />
cos x= 0 ⇒ x= + kπ<br />
2<br />
cos x= 1⇒ x=<br />
2kπ<br />
[ ] ( )<br />
k<br />
{ π }<br />
sin x= a∈−1,1 ⇒ S = − 1 arcsin a+ k / k∈<br />
[ ] { π }<br />
{ π / }<br />
{ π / }<br />
cos x= a∈−1,1 ⇒ S = ± arccos a+ 2 k / k∈<br />
T R A I A N<br />
tgx = a ⇒ S = arctga + k k ∈<br />
ctgx = a ⇒ S = arcctga + k k ∈<br />
4