3*sin2x+cos2x=2sinx;Chia 2 v cho 2 3 / 2.sin2x + 1/2.cos2x = sinx sin(pi/3).sin(2x) + cos(pi/3).cos(2x) = sinx cos(2x-pi/3) = sinx cos(2x-pi/3) = cos (pi/2 x)-------------(((-------------

1+sinx+cosx+sin2x+cos2x=0

Phng trnh cho tng ng vi:

INCLUDEPICTURE "http://boxmath.vn/cgi-bin/mimetex.cgi?%5Cblue%20%7B%28%5Csin%20x%20+%20%5Ccos%20x%29%5E2%7D%20+%20%28%5Csin%20x%20+%20%5Ccos%20x%29%20+%20%28%5Ccos%20x%20-%20%5Csin%20x%29%28%5Ccos%20x%20+%20%5Csin%20x%29%20=%200" \* MERGEFORMATINET

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cos(2x) = cos x + sin x=> cos^2(x) - sin^2(x) = cos x + sin x=> ( cos x + sin x)(cos x - sin x) = (cos x + sin x)=> ( cos x + sin x)(cos x - sin x) - (cos x + sin x) = 0=> (cos x + sin x )(cos x - sin x - 1) = 0TH1.cos x + sin x = 0cosx = -sin xtan x = - 1=>x = 3/4, 7/4TH2.cos x - sin x - 1 = 0cos x - sin x = 1cos^2(x) + sin^2(x) - 2sin x cos x = 11 - sin(2x) = 1sin(2x) = 02x = 0, , 2x = 0, /2, x = 0, 3/4, 7/4 trong khong [ 0, 2 ]

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Bi 2:Cho hnh chp S.ABCD c y l hnh thang, AB l y ln.Gi I,J,K ln lt l cc im trn cc cnh SA, SB, BC.a/Tm giao tuyn 2 mp(SAK) v (SBD).b/Tm giao im ca IK vi mp(SBD).c/Tm giao im ca SC, SD vi mp(I JK).d/Xc nh thit din ca mp(I JK) vi t din SABC.GiiBi 2: a) xt mp ABCD th gi DBAK= Ldo BD thuc mp SBD , AK thuc mp SAK L thuc giao tuyn chung , kt hp im S cng th nn giao tuyn l SL

b) Do IK thuc mp SAK nn IK ct mp SBD s i qua dao tuyn nn tip im l IKSL

c)xt mp SBC gi SCJK= P (1)JK thuc mp IJK nn tip im l P IK thuc mp SAK gi AKDC =Qth giao tuyn ca mp SAK v mp SDC l SQ IJ s ct giao tuyn SQ m ta gi l U (2)t (1) v (2) giao tuyn ca mp SDC v mp IJK l PU vy tip im SD v mp IJK l giao im ca SD vi PU d)xt mp IJK , mp ABCD , mp SAB c 2 giao tuyn l IJ v AB nu bn ly I v J bt k m IJ ct AB th giao tuyn cng li cng ct ti giao im v i qua K , cn nu IJ song song th giao im cn li i qua K v song song vi AB . V ta gi giao tuyn ct AB ti H Vy tit din l IJKH

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Ch dng qu tm phn bit cc dung dch sau: Bit rng cc dung dch n nng khng qu long:

a. Na2SO4, Na2CO3, BaCl2, KNO3.

b. NH4Cl, (NH4)2SO4, BaCl2, NaOH, Na2CO3.

Gii

Ch dng qu tm phn bit cc dung dch sau: Bit rng cc dung dch n nng khng qu long:

a. Na2SO4, Na2CO3, BaCl2, KNO3. Trch mu, cho vo cc l v nh s. Cho qu vo 4 l dung dch --> ha xanh : Na2CO3, cho Na2CO3 vo 3 l dung dch cn li --> kt ta : BaCl2. Cho BaCl2 vo hai dung dch cn li --> kt ta : Na2SO4, cn li l l KNO3

b. NH4Cl, (NH4)2SO4, BaCl2, NaOH, Na2CO3.: cho qu vo--> ha xanh: NaOH, Na2CO3; ha hng: NH4Cl, (NH4)2SO4. cn li l BaCl2. Cho BaCl2 vo tng cp l dung dch th s ra kt qu :))

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Ch dng qu tm: kali photphat; amoni clorua; bari nitrat; kali nitrat:Gii

Dung dch K3PO4 c mi trng baz lm i mu qu tm thnh xanh. C th dng qu tm phn bit.

qu tm lm NH4Cl chuyn mu v y l cht to bi ion ca baz yu v axt mnh.-------------(((-------------

Cho Na vo dung dch Al2(SO4)3 b/ Cho K vo dung dch FeSO4Ban u c kt ta "huyn ph" ri tan dn, tip tc nh Al2(SO4)2 c kt ta trng.V c phn ng:Al2(SO4)3 + 6NaOH(d) --> 2Al(OH)3 + 3Na2SO4Al(OH)3 + NaOH --> NaAlO2 + 2H2O

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Cho hnh chp S. ABCD y l t gic li. Gi E l trung im SA, F l trung im thuc cnh SB sao cho SF=1/3SB v G l trng tm tam gic BCD.

a/ CM: FG // mp (SCD);

b/ Xc nh giao tuyn gia mp (SAD) v mp (EFG);

c/ Xc nh giao im H ca ng thng CD v mp (EFG);

d/ Xc nh thit din ca hnh chp vi mp (EFG)

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Trong mp Oxy cho ng trn (C) c pt: x2 +y2 4x + 6y -3 = 0. Tm nh ca (C ) qua php ng dng c c bng cch thc hin lin tip php i xng trc Ox v php i xng tm I ( 2, -3).-------------(((-------------

T cc s {0, 1, 2, , 6} c th lp c bao nhiu s t nhin gm 4 ch s i 1 khc nhau. Chn ngu nhin 1 s t nhng s va lp c, tnh xc sut s c chn l s chn.

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T CaCO3, khng kh, NaCl, iu ch phn Ur:

Gii:

+ Khng kh bao gm: kh O2, CO2, N2, Ar (b qua hidro)1) Khng kh :+ Loi b CO2 bng cch cho qua NaOH+ Loi b hi nc dng nc nhit -25*C-> To thnh khng kh kh khng c CO22) Ha lng khng kh -> Khng kh lng3) Khng kh lng : chng ct phn on thu c:+ O2 nhit -183*C+ Ar nhit -186*C+ N2 nhit -196*C

+ iu ch phn m 2 l:a) H2O -> H2 + 1/2O2 (in phn dung dch)

Cho N2 tc dng vi H2: N2 + 3H2 -> 2NH3 (xc tc platin Pt, to)

t NH3 vi O2 thu NO:4NH3 + 5O2 -> 4NO + 6H2O (xc tc platin Pt, to)

NO ha nu trong O2 to NO2:NO + 1/2 O2 -> NO2

NO2 tc dung vi oxi, H2O to HNO3:4NO2 + O2 + 2H2O -> 4HNO3

HNO3 tc dng vi NH3 to NH4NO3NH3 + HNO3 -> NH4NO3.

b) Phn ur:CaCO3 -> CaO + CO2 (to)CO2 + 2NH3 -> (NH2)2CO + H2O (p sut cao, nhit cao)

(Nh bn u tin tr li u c cacbon (C) u m cho phn ng vi H2O)

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1) Hp cht hu c A cha C , H , O , N c M = 89 .t chy 1 mol A thu c 3 mol C , 0.5 mol N2 v hi H2O . Tm CTPT ca A .Gii:

2) Oxi ha hon ton mt Hydrocacbon X cn dng 6.72 lt O2 m thu c 4.48 lt CO2 . Tm CTPT

Gii:

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sinx^4+sin(x+/4)^4+sin(x-/4)^4=5/4-------------(((-------------

Tr ln gi rihttp://www.wolframalpha.com/input/?i=(%E2%88%9A(x%2B6)-2x%2B3)%2F(x^3-3x^2)%2C+x--%3E3 http://www.wolframalpha.com/input/?i=(x^2-8)%2F(%E2%88%9A(2x%2B5)%2Bx-5)%2C+x--%3E2 http://www.wolframalpha.com/input/?i=(1%2Ftan386)+%2B+(2sin2550cos-188)%2F(2cos638+%2B+cos98) (1/tan386) + (2sin2550cos-188)/(2cos638 + cos98)http://www.wolframalpha.com/input/?i=cot(13%CF%80%2F90)-+cot(2%CF%80%2F45) cot(13/90)- cot(2/45)