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  lOMoAR cPSD| 49519085 Tr°ờng THPT MARIE CURIE    Chuyên Á 1  
PH¯¡NG TRÌNH L¯þNG GIÁC      
XÁC ĐÞNH GIÁ TRÞ L¯þNG GIÁC       lOMoAR cPSD| 49519085
ChuyŒn đề 1: L¯þNG GIÁC    CĂA MÞT G  C HAY CUNG L¯þNG GIÁC  ✓   
1 . аßng tròn l°ÿng giác   
 Là đ°ờng tròn có   t m O trong mặt phẳng Oxy v c bÆn k nh R 1 .   Aø  1 ;0  ù
 là điểm gốc của đ°ờng tròn l°ÿng giác. 
 Chiều d°¡ng là chiều ng°ÿc chiều kim đồng hồ. 
 Chiều âm là chiều cùng chiều kim đồng hồ.    2. G  
iá trß l°ÿng giác    Cho cung AM   sin OK  
 Tung độ của điểm M .   Cos = cos OH  
 Hoành độ của điểm M .    sin tan    AT     t At tại T )  c  
 (KØo d i OM cắt tiếp tuyến ’  os    cos     cot    0 ; 1 )  s  
 (KØo d i OM cắt tiếp tuyến ’ 
s Bs tại S , với ø ù in  B  B           2       lOMoAR cPSD| 49519085 Tr°ờng THPT MARIE CURIE          lOMoAR cPSD| 49519085
ChuyŒn đề 1: L¯þNG GIÁC        
CÔNG THþC L¯þNG GIÁC ✓  1. Hß thÿc c¢ bÁn   1 tan2 a   12  tana   1   sin2 a cos2 a   1cos a   tan .cota  a  1cota  1 cot2 a   12  cota   1  sin atana       tana
sina sina  tan cosa  a     cota
cosa cosa  cot .sina  
a cosa sina  2. Cung liŒn k¿t   3. C ng thÿc cßng  
 sin(a b  ) sin cosa  b sin cosb  a  cos( a) cosa  sin(  a) sina    sin(  a) sina 
cos(a  b) cos cosa  b  sin sina cos(   a) cosa  tan(  a) tana    b  tan(   a) tana  cot(  a) cota   cot(   a) cota       4       lOMoAR cPSD| 49519085 Tr°ờng THPT MARIE CURIE    ö ö  ö ö 
 tan(a b  ) tana  tanb 
sin÷ a÷ cosa ø 2
sin÷ a÷ cosa ø 2   1 tan .tana b    ø    ø  ö ö  ö ö   cot(a b  )   
cos÷ a÷ sina ø  cos÷ a÷ sina ø     2 ø ö ö  2 ø ö ö 
tan÷ a÷ cota ø 2
`p dāng c ng thÿc cßng ta °ÿc   tan÷ a÷ cota ø 2   ø    ø  ö ö  ö ö  ö ö
sinx cosx  2 sin÷x  ÷    
cot÷ a÷ tana ø 2 ø cot÷ a÷ tana ø 2   ø   4 ø ö    ø  ö 
cosx sinx  2 cos÷x  ÷     ø 4 ø  …   4. Cung liŒn k¿t  
5. C ng thÿc nhân ôi  
 sin2a 2sin cosa a  sin(   a) sina  sinøa ù sina  cos2 a–sin2 a  cos(   a) cosa  cosøa   ù tan( a) tana 
 cos2a  1 2sin2 a   cot(   a) cota  cosa tanøa   ù  2cos2 a 1  tana cotøa   ù   tan2a  2tana2    cota   1 tan a 
sin÷ a÷ cosa cosö÷
aö÷ sina ö ö   cot2a   1   1 tan2 a tan2a   ø 2 ø  ø 2 ø    2tana 
tan÷ a÷ cota cotö÷
aö÷ tana ö ö       ø 2 ø  ø 2 ø  6.C ng thÿc h¿ b¿c  
sinøa k  .2 ù sina cosøa k  .2 ù cosa *sin2 a  
1 cos2a 1cos2a  2sin2 a  2 
tanøa k  ù tana cotøa k  ù cota  *cos2 a  
1 cos2a 1cos2a  2cos2 a   2  *tan2 a    1  cos2a  1  cos2a      lOMoAR cPSD| 49519085
ChuyŒn đề 1: L¯þNG GIÁC   
7. C ng thÿc bi¿n t ch th nh táng *cos 
8.C ng thÿc bi¿n táng th nh t ch     
.cosa b  ù ûcos(a b  ) cos(a b  ù)û 
*cosa  cosb  2cos÷a b  ö÷cosö÷a b    ù ö÷ ö    *sin .sina b 1 ûcos(a b  )   ø 2 ø  ø 2 ø   cos(a b  ù)û      cosa  cosb
2sinö÷a b  ö÷sinö÷a b   *sin .cosa 
b  ùûsin(a b  ) sin(a  b  ù)û 2  ö÷    ø 2 ø  ø 2 ø   ù *cos .sina  b 1 ûsin(a b  ) ö    sin(a b  ù)û 2 
*sina  sinb  2sin÷a b  ö÷cosö÷a b  ö÷     ø 2 ø  ø 2 ø 
 sina  sinb  2cosö÷a b  ö÷sinö÷a b  ö÷    ø 2 ø  ø 2 ø  *tana  tanb   sin(a  b  ) cos cosa  b    
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PH¯¡NG TRÌNH L¯þNG GIÁC C¡ BÀN ✓     A. PH¯¡NG PH`P          6       lOMoAR cPSD| 49519085 Tr°ờng THPT MARIE CURIE     1.  radian ù   u v k2    æo ùu v k  3600  hoặc    sinu  sinv ú  0  0 ,k  
sinu  sinv  úû   v k2 ,k  
úûu  180 v k360   æo ùu  u  radian ù   u v k2 
cosu  cosv  úû   v k2 ,k   u  v k  3600 
 2. hoặc cosu  cosv ú  0 ,k    úûu  v k360   
radian tanu  tanv  
æo tanu  tanv u v 
 3. u v k , k  
 hoặc k  1800, k    
radian cotu  cotv  
æo cotu  cotv u v k  
 4. u v k , k    hoặc 1800, k     radian   
ù x arcsinm k  2  sinx m  úû 
 arcsinm k  2 ,k   ĐẶC  x  BIÞT         radian   sinu  
ù x arccosm k  2  1  u cosx  m  úû 
arccosm k  2 ,k     k2  x    2      radian   sinu  
tanx m  x arctanm k  , k    1       radian  u  k2 
cotx m  x arccotm k  , k     2   sinu   0  u k      cosu   1 u k2   cosu   1 u  k2        lOMoAR cPSD| 49519085
ChuyŒn đề 1: L¯þNG GIÁC       cosu    5.  0          u  k   2   6.              7.              8.     
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..................................................................................................................................................................  B. VÍ DĀ     ö ö      8       lOMoAR cPSD| 49519085 Tr°ờng THPT MARIE CURIE     
Ví dā 1. Giải ph°¡ng trình sin÷x ÷ sin 2 .    ø 2 ø  5    Lßi giÁi    
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Ví dā 2. Giải ph°¡ng trình sinøx 30 ù 0  sin200 .    Lßi giÁi    
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Ví dā 3. Giải ph°¡ng trình sinxøcosx  2ù 0    Lßi giÁi    
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Ví dā 4. Giải ph°¡ng trình 2sinx 1.    Lßi giÁi       lOMoAR cPSD| 49519085
ChuyŒn đề 1: L¯þNG GIÁC     
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Ví dā 5. Giải ph°¡ng trình sin÷x ÷ 1.    ø 5 ø    Lßi giÁi  
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Ví dā 6. Giải ph°¡ng trình 2sin÷x ÷ 2 0 .    ø 6 ø    Lßi giÁi    
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Ví dā 7. Giải ph°¡ng trình 2sinøx 60 ù 0  3 0 .        10       lOMoAR cPSD| 49519085 Tr°ờng THPT MARIE CURIE    Lßi giÁi    
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Ví dā 8. Giải ph°¡ng trình sin3x  cos÷öø x  3 ö÷ø .    Lßi giÁi    
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Ví dā 9. Giải ph°¡ng trình cos 2÷öø x  ö÷ø     sin÷øö  x  4  öø÷ .    5    Lßi giÁi    
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Ví dā 10. Giải ph°¡ng trình 5sinx 1 .        lOMoAR cPSD| 49519085
ChuyŒn đề 1: L¯þNG GIÁC    Lßi giÁi    
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Ví dā 11. Giải ph°¡ng trình sinøx 2ù  .    Lßi giÁi    
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Ví dā 12. Giải ph°¡ng trình cos÷x 2 ö÷ cos .  ö    ø  5 ø  7    Lßi giÁi    
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Ví dā 13. Giải ph°¡ng trình cosøx 40 ù 0  cos100 .    Lßi giÁi       12       lOMoAR cPSD| 49519085 Tr°ờng THPT MARIE CURIE     
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Ví dā 14. Giải ph°¡ng trình 2cosx 1 .    Lßi giÁi    
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Ví dā 15. Giải ph°¡ng trình cos÷x ÷ 1 .    ø 8 ø    Lßi giÁi    
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Ví dā 16. Giải ph°¡ng tr nh 2cos÷x ÷ 3 0 .    ø 6 ø    Lßi giÁi    
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ChuyŒn đề 1: L¯þNG GIÁC     
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Ví dā 17. Giải ph°¡ng trình 2cosøx  30 ù 0  2 0 .    Lßi giÁi    
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Ví dā 18. Giải ph°¡ng trình 3cosx  3  0 .    Lßi giÁi    
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Ví dā 19. Giải ph°¡ng trình 5cosø2x  1ù 30 .  Lßi giÁi    
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Ví dā 20. Giải ph°¡ng trình tan÷x 3 ö÷ tan .  ö    ø  4 ø  7    Lßi giÁi    
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Ví dā 21. Giải ph°¡ng trình tanøx  48 ù 0  tan250 .    Lßi giÁi    
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Ví dā 22. Giải ph°¡ng trình tanx  3 .    Lßi giÁi    
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Ví dā 23. Giải ph°¡ng trình tan÷ x÷ cot  .    ø 6 ø  6        lOMoAR cPSD| 49519085
ChuyŒn đề 1: L¯þNG GIÁC    Lßi giÁi    
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Ví dā 24. Giải ph°¡ng trình tanøx  30 ù 0  10.    Lßi giÁi    
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Ví dā 25. Giải ph°¡ng trình 2tanx  5 0.    Lßi giÁi    
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Ví dā 26. Giải ph°¡ng trình cot÷x ÷ cot  .    ø 8 ø  5    Lßi giÁi    
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Ví dā 27. Giải ph°¡ng trình cotøx  28 ù 0  cot120 .    Lßi giÁi    
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Ví dā 28. Giải ph°¡ng trình 3cotx  3  0.    Lßi giÁi    
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Ví dā 29. Giải ph°¡ng trình cot÷x ÷ 1 0 .    ø 6 ø    Lßi giÁi    
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ChuyŒn đề 1: L¯þNG GIÁC     
Ví dā 30. Giải ph°¡ng trình cot 2ø x  20 ù o  3 0.    Lßi giÁi    
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Ví dā 31. Giải ph°¡ng trình 3cotx  5 0 .    Lßi giÁi    
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Ví dā 32. Giải ph°¡ng trình cosx sinx 0.    Lßi giÁi    
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Ví dā 33. Giải ph°¡ng trình 3sinx cosx  0.    Lßi giÁi       18       lOMoAR cPSD| 49519085 Tr°ờng THPT MARIE CURIE     
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Ví dā 34. Giải ph°¡ng trình 3cosx sinx  0.    Lßi giÁi    
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Ví dā 35. Giải ph°¡ng trình sin2x sin2 cosx x 0.    Lßi giÁi    
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Ví dā 36. Giải ph°¡ng trình cosx 2sin2 x 0 .  2    Lßi giÁi    
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ChuyŒn đề 1: L¯þNG GIÁC     
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Ví dā 37. Giải ph°¡ng trình sin3x sinx 0 .    Lßi giÁi    
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Ví dā 38. Giải ph°¡ng trình cos4x sinx .    Lßi giÁi    
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Ví dā 39.  Ph°¡ng trình 2cos2 x  1 0 có bao nhiêu nghiệm trên đoạn ú 3 ; ú .    û 2 2 û    Lßi giÁi    
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