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7/24/2019 Luong Giac Maths287
1/21
Nguyn
MinhT
in-m
aths287
maths287 CHUYN LNG GIC
BI GING 00 : H THC LNG GIC C BN
Gio vin : Nguyn Minh Tin - maths287
H thc lng gic c bn
sin2 + cos2 = 1
tan = sin cos
cot = cos sin
tan . cot = 1
1 + tan2 = 1cos
1 + cot2 = 1sin2
V D MINH HA
V d 1 : Tnh gi tr lng gic cn li ca mt gc bit
sin = 14
vi gc nhn
cos =13
tan = 2
2
cos = 513
vi90o <
7/24/2019 Luong Giac Maths287
2/21
Nguyn
MinhT
in-m
aths287
maths287 CHUYN LNG GIC
V d 5 : Chng minh cc ng thc sau
a. tan x + cot x= 1
sin x cos x
b. 11 + tan x+ 1
1 + cot x= 1
c.1 + sin2 x
1 sin2 x = 1 + 2 tan2 x
d. 1 cot4 x= 2sin2 x
1sin4 x
e. (1 cos x)
1 + cot2 x
= 11 + cos x
f. sin x
1 + cos x+
1 + cos x
sin x =
2
sin x
V d 6 : Chng minh cc ng thc sau
a. sin6 x + cos6 x= 1 3sin2 x cos2 x
b. sin6 x cos6 x=
sin2 x cos2 x
1 sin2 x cos2 x
c. sin8 x + cos8 x=
1 2sin2 x cos2 x2 2sin4 x cos4 xd. sin8 x cos8 x=
sin2 x cos2 x
1 2sin2 x cos2 x
V d 7 : Chng minh cc ng thc sau
a. sin2 x cos2 x1 + 2 sin x cos x
= tan x 1tan x + 1
b. cos2 x
1 tan x + sin2 x
1 cot x = 1 sin x cos x
c. 1
sin2 x cos2 x= tan2 x + cot2 x + 2
d. tan2 x tan2 y
tan2 x tan2 y =
sin2 x sin2 ysin2 x sin2 y
V d 8 : Bin i cc biu thc sau thnh tch s
A = 2cos2 x 1
B = 3 4sin2 x
C = sin x cos x + cos2 x 1
D = sin2 x + sinx cos x 1
E = 1 + sin x + cos x + tan x
F = tanx cot x + sin x + cos x
G = cosxtan2 x (1 + cos x)
H =
3 4cos2 x sinx (2sin x + 1)
V d 9 : Rt gn cc biu thc sau
A = sin4 x + sin2 xcos2 x
B = sin2 x + cot2 xsin2 x
C =
1 sin2 x
cot2 x + 1 cot2 x
D = sin4 x cos4 x + cos2 x
E = cos2 x + cos2 xcot2 x
F = sin2 x tan x + cos2 x cotx + 2 sin x cos x
V d 10 : Chng minh cc biu thc sau khng ph thuc vo bin x
A = cos4 x sin4 x + 2 sin2 x
B = sin4 x + sin2 xcos2 x + cos2 x
C = cos4 x + sin2 xcos2 x + sin2 x
D = cos4 x
2cos2 x 3
+sin4 x
2sin2 x 3
E = sin6 x + cos6 x 2sin4 x cos4 x + sin2 x F = cos2 xcot2 x + 5 cos2 x cot2 x + 4 sin2 x
Bi ging : H thc lng gic c bn 2
7/24/2019 Luong Giac Maths287
3/21
Nguyn
MinhT
in-m
aths287
maths287 CHUYN LNG GIC
BI TP LUYN TP
Luyn tp 1 : Chng minh cc ng thc sau
a. 1 cos xsin x = sin x1 + cos x
b.
1 1cos x
1 +
1
cos x
+ tan2 x= 0
c. tan x tan y =tan x + tan y
cot x + cot y
d. tan x + cos x
1 + sin x=
1
cos x
e.1 + cos x
1
cos x 1 cos x
1 + cos x =
4cot x
sin x
f. sin x + cos x 1
sin x cos x + 1 = cos x
1 + sin x
g. sin x + cos x 11 cos x = 2cos xsin x cos x + 1
h. tan2 x sin2 x
cot2 x cos2 x = tan6 x
i. tan x sin x
sin3 x=
1
cos x (1 + cos x)
j. 1
cos2 x tan2 x= 3tan
2 x
cos2 x + 1
k. 1 cos xsin x
(1 + cos x)2
sin2 x 1
= 2 cot x
Luyn tp 2 : Rt gn cc biu thc sau
A = 2cos2 x 1
sin x + cos x
B = cot x + cot ytan x + tan y
C = sin x + tan x
tanx sinxcotx
D =cos2 x cot2 x
sin2 x tan2 x
E =sin3 x + sin x cos2 x cosx
1 2sinxcosx
F = sin2 x + sin2 xtan2 x
cos2 x + cos2 xtan2 x
G = cos2 x sin2 y
sin2 xsin2 y cot2 xcot2 y
H =1 cosxsinx
+1 sinx
cosx + tan x + cot x
I = 1 cosxsin2 x 11 + cos x
J = tanx + cosx1 + sin x
K =cos x tan xsin2 x
cotxcosx
L = 1 sin2 xcos2 x
cos2 x cos2 x
Luyn tp 3 : Chng minh cc biu thc sau khng ph thuc vo bin x
A = 2tanx 1+
cot x + 1
cotx 1
B =
1 tan2 x2
4tan2 x 1
4sin2 xcos2 x
C = 1 tan2 x
tanx
1 + tan2 x
1 + cot2 x
D =
1 cot2 x2
cot2 x 1
sin2 xcos2 x
E =1 sin6 x
cos6 x 3tan
2 x
cos2 x
F = tan2 x cos2 x
sin2 x +
cot2 x sin2 xcos2 x
G = cot2 x cos2 x
cot2 x +
sin x cos x
cos2 x
H =sin4 x + cos4 x 1
sin6 x + cos6 x
Bi ging : H thc lng gic c bn 3
7/24/2019 Luong Giac Maths287
4/21
Nguyn
MinhT
in-m
aths287
maths287 CHUYN LNG GIC
CNG THC CNG
sin(a + b) = sin a cos b + sin b cos a
cos(a + b) = cos a cos b sin a sin b
tan(a + b) = tan a + tan b1 tan a tan b
sin(a b) = sin a cos b sin b cos a
cos(a b) = cos a cos b + sin a sin b
tan(a b) = tan a tan b1 + tan a tan b
H qu
tan
4+ a
=
1 + tan a
1 tan a tan
4 a
=
1 tan a1 + tan a
V D MINH HA
V d 1 : Khng dng my tnh, hy tnh gi tr cc biu thc
A = sin 12o. cos 48o + cos 12o. sin48o
B = cos 38o. cos 22o sin38o. sin 22o
C = sin 10o. cos55o cos10o. sin 55o
D = sin36o. cos6o sin126o. cos84o
E = cos 112o. cos23o sin112o. sin 23o
F = sin 200o. sin 310o + cos340o. cos50o
G = cos11o. cos 21o +cos69o. cos79ocos 10o
H = cos68o. cos 78o+cos22o. cos 12osin 100o
V d 2 : Tnh gi tr cc biu thc sau
A =1 + tan 15o
1 tan15o
B = sin 10o. cos20o + sin 20o. cos 10o
cos17o. cos 13o sin17o. sin 13o
C = sin73o. cos3o sin 87o. cos17o
cos 132o. cos62o + cos 42o. cos 28o
D = cos2 75o sin2 75o
E = tan25o + tan 20o
1 tan25o. tan 20o
F = tan 225o cot81o. cot69o
cot 261o + tan 201o
G = cot 225o cot79o. cot71o
cot 259o + cot 251o
H = tan 20o. tan 80o + tan80o. tan 140o +tan 20o. tan 140o
V d 3 : Tnh gi tr cc biu thc sau
A = cos
x +
3
bit sin x=
13
v0 < x <
2
B = sin
3 x
bit cos x=12
13v < x