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Question Number 110260    Answers: 1   Comments: 0

lim_(x→∞) x cos ((1/x)) ?

$$\underset{{x}\rightarrow\infty} {\mathrm{lim}}\:{x}\:\mathrm{cos}\:\left(\frac{\mathrm{1}}{{x}}\right)\:? \\ $$

Question Number 110254    Answers: 1   Comments: 0

Given tan α and tan β are the two roots of 2x^2 −x−2=0, then sin(2α+2β)+cos(2α+2β)+tan(2α+2β)=?

$$\mathrm{Given}\:\mathrm{tan}\:\alpha\:\mathrm{and}\:\mathrm{tan}\:\beta\:\mathrm{are}\:\mathrm{the}\:\mathrm{two}\:\mathrm{roots}\: \\ $$$$\mathrm{of}\:\mathrm{2}{x}^{\mathrm{2}} −{x}−\mathrm{2}=\mathrm{0},\:\mathrm{then} \\ $$$$\mathrm{sin}\left(\mathrm{2}\alpha+\mathrm{2}\beta\right)+\mathrm{cos}\left(\mathrm{2}\alpha+\mathrm{2}\beta\right)+\mathrm{tan}\left(\mathrm{2}\alpha+\mathrm{2}\beta\right)=? \\ $$

Question Number 110247    Answers: 1   Comments: 0

Let f(x) = ∫_0 ^( x) e^(−t) dt then f ′′(x) = ??

$$\mathrm{Let}\:{f}\left({x}\right)\:=\:\int_{\mathrm{0}} ^{\:{x}} {e}^{−{t}} {dt}\: \\ $$$$\mathrm{then}\:{f}\:''\left({x}\right)\:=\:?? \\ $$

Question Number 110246    Answers: 1   Comments: 0

solve for z∈C: (a+bi)^z =b+ai

$${solve}\:{for}\:{z}\in\mathbb{C}:\:\left({a}+{bi}\right)^{{z}} ={b}+{ai} \\ $$

Question Number 110245    Answers: 1   Comments: 2

solve ∫(dx/( ((c−(√(b−ax))))^(1/3) ))

$${solve}\:\int\frac{{dx}}{\:\sqrt[{\mathrm{3}}]{{c}−\sqrt{{b}−{ax}}}} \\ $$

Question Number 110233    Answers: 0   Comments: 0

Question Number 110227    Answers: 1   Comments: 1

Question Number 110223    Answers: 0   Comments: 4

let :A,B,C,D be anone empety set prove that A×B=C×D↔A=C∧B=D ? help me sir

$${let}\::{A},{B},{C},{D}\:{be}\:{anone}\:{empety}\:{set}\:{prove}\:{that}\: \\ $$$${A}×{B}={C}×{D}\leftrightarrow{A}={C}\wedge{B}={D}\:? \\ $$$${help}\:{me}\:{sir} \\ $$

Question Number 110222    Answers: 3   Comments: 0

find the series Σ_(n=2) ^∞ (−1)^n [(1/(3n+1))+(1/(3n−2))]

$${find}\:{the}\:{series} \\ $$$$\underset{{n}=\mathrm{2}} {\overset{\infty} {\sum}}\left(−\mathrm{1}\right)^{{n}} \left[\frac{\mathrm{1}}{\mathrm{3}{n}+\mathrm{1}}+\frac{\mathrm{1}}{\mathrm{3}{n}−\mathrm{2}}\right] \\ $$

Question Number 110219    Answers: 0   Comments: 3

let A and C be two none empety set prove that A⊆B ∧ C ⊆D iff A×C ⊆B×D? help me sir

$${let}\:{A}\:{and}\:{C}\:{be}\:{two}\:{none}\:{empety}\:{set}\:{prove}\:{that} \\ $$$${A}\subseteq{B}\:\wedge\:{C}\:\subseteq{D}\:{iff}\:{A}×{C}\:\subseteq{B}×{D}? \\ $$$${help}\:{me}\:{sir} \\ $$

Question Number 110218    Answers: 1   Comments: 0

Question Number 110215    Answers: 1   Comments: 1

Question Number 110214    Answers: 1   Comments: 0

show that ∫_(−∞) ^(+∞) (((1+(x/π))sin(πx))/(x^2 +4x+5))dx=(1/e^π )

$${show}\:{that}\: \\ $$$$\int_{−\infty} ^{+\infty} \frac{\left(\mathrm{1}+\frac{{x}}{\pi}\right)\mathrm{sin}\left(\pi{x}\right)}{{x}^{\mathrm{2}} +\mathrm{4}{x}+\mathrm{5}}{dx}=\frac{\mathrm{1}}{{e}^{\pi} } \\ $$

Question Number 110204    Answers: 1   Comments: 4

Question Number 110203    Answers: 1   Comments: 0

Question Number 110197    Answers: 2   Comments: 4

(−1)^π =? (−1)^((22)/7) =(−1)^(3+(1/7)) =(−1)^3 .(−1)^(1/7) =−(−1)^(1/7) let (−1)^π =t ⇒−(−1)^(1/7) =t ⇒(−1)^(1/7) =−t ⇒(−1)=(−t)^7 ⇒−1=−t^7 ⇒1=t^7 hence t=1 ∴(−1)^π =1 i request all math professionals to check this and if any error then pls comment.

$$\left(−\mathrm{1}\right)^{\pi} =? \\ $$$$\left(−\mathrm{1}\right)^{\frac{\mathrm{22}}{\mathrm{7}}} \\ $$$$=\left(−\mathrm{1}\right)^{\mathrm{3}+\frac{\mathrm{1}}{\mathrm{7}}} \\ $$$$=\left(−\mathrm{1}\right)^{\mathrm{3}} .\left(−\mathrm{1}\right)^{\frac{\mathrm{1}}{\mathrm{7}}} \\ $$$$=−\left(−\mathrm{1}\right)^{\frac{\mathrm{1}}{\mathrm{7}}} \\ $$$${let}\:\left(−\mathrm{1}\right)^{\pi} ={t} \\ $$$$\Rightarrow−\left(−\mathrm{1}\right)^{\frac{\mathrm{1}}{\mathrm{7}}} ={t} \\ $$$$\Rightarrow\left(−\mathrm{1}\right)^{\frac{\mathrm{1}}{\mathrm{7}}} =−{t} \\ $$$$\Rightarrow\left(−\mathrm{1}\right)=\left(−{t}\right)^{\mathrm{7}} \\ $$$$\Rightarrow−\mathrm{1}=−{t}^{\mathrm{7}} \\ $$$$\Rightarrow\mathrm{1}={t}^{\mathrm{7}} \\ $$$${hence}\:{t}=\mathrm{1} \\ $$$$\therefore\left(−\mathrm{1}\right)^{\pi} =\mathrm{1} \\ $$$$\boldsymbol{{i}}\:\boldsymbol{{request}}\:\boldsymbol{{all}}\:\boldsymbol{{math}} \\ $$$$\boldsymbol{{professionals}}\:\boldsymbol{{to}}\: \\ $$$$\boldsymbol{{check}}\:\boldsymbol{{this}}\:\boldsymbol{{and}}\:\boldsymbol{{if}} \\ $$$$\boldsymbol{{any}}\:\boldsymbol{{error}}\:\boldsymbol{{then}}\:\boldsymbol{{pls}} \\ $$$$\boldsymbol{{comment}}. \\ $$

Question Number 110183    Answers: 3   Comments: 0

(√★)((be)/(math))(√★) log _2 (x)+log _3 (x)+log _4 (x)=1 x=?

$$\:\:\:\sqrt{\bigstar}\frac{{be}}{{math}}\sqrt{\bigstar} \\ $$$$\:\:\mathrm{log}\:_{\mathrm{2}} \left({x}\right)+\mathrm{log}\:_{\mathrm{3}} \left({x}\right)+\mathrm{log}\:_{\mathrm{4}} \left({x}\right)=\mathrm{1} \\ $$$$\:\:\:{x}=? \\ $$

Question Number 110182    Answers: 1   Comments: 2

Solve x^3 +15x−92=0

$$\mathrm{Solve}\:{x}^{\mathrm{3}} +\mathrm{15}{x}−\mathrm{92}=\mathrm{0} \\ $$

Question Number 110175    Answers: 2   Comments: 0

solve the integral ∫_(−∞) ^(+∞) ((sinx)/(x)^(1/3) )dx

$${solve}\:{the}\:{integral} \\ $$$$\int_{−\infty} ^{+\infty} \frac{\mathrm{sin}{x}}{\sqrt[{\mathrm{3}}]{{x}}}{dx} \\ $$

Question Number 110173    Answers: 2   Comments: 0

If Σ_(r=1) ^n t_r =((n(n+1)(n+2)(n+3))/8) then lim_(n→∞) Σ_(r=1) ^n (1/t_r ) = ?

$${If}\:\:\underset{{r}=\mathrm{1}} {\overset{{n}} {\sum}}{t}_{{r}} =\frac{{n}\left({n}+\mathrm{1}\right)\left({n}+\mathrm{2}\right)\left({n}+\mathrm{3}\right)}{\mathrm{8}} \\ $$$${then}\:\:\:\:\underset{{n}\rightarrow\infty} {\mathrm{lim}}\:\:\underset{{r}=\mathrm{1}} {\overset{{n}} {\sum}}\:\frac{\mathrm{1}}{{t}_{{r}} }\:=\:? \\ $$$$ \\ $$

Question Number 110157    Answers: 2   Comments: 0

If we have 5 people, how many ways can they be seated on a round table, if there are, (a) 7 chairs (b) 3 chairs available

$$\mathrm{If}\:\mathrm{we}\:\mathrm{have}\:\:\mathrm{5}\:\:\mathrm{people},\:\mathrm{how}\:\mathrm{many}\:\mathrm{ways}\:\mathrm{can}\:\mathrm{they}\:\mathrm{be}\:\mathrm{seated} \\ $$$$\mathrm{on}\:\mathrm{a}\:\mathrm{round}\:\mathrm{table},\:\mathrm{if}\:\mathrm{there}\:\mathrm{are}, \\ $$$$\left(\mathrm{a}\right)\:\:\:\mathrm{7}\:\:\mathrm{chairs}\:\:\:\:\:\:\:\:\:\left(\mathrm{b}\right)\:\:\:\:\mathrm{3}\:\:\mathrm{chairs}\:\:\:\:\:\:\:\:\:\:\:\mathrm{available} \\ $$

Question Number 110156    Answers: 1   Comments: 0

If we have 5 people, how many ways can they be seated in a row on a chair, if their are, (a) 7 chairs (b) 3 chairs available

$$\mathrm{If}\:\mathrm{we}\:\mathrm{have}\:\:\mathrm{5}\:\mathrm{people},\:\mathrm{how}\:\mathrm{many}\:\mathrm{ways}\:\mathrm{can}\:\mathrm{they}\:\mathrm{be}\:\mathrm{seated}\:\mathrm{in}\:\mathrm{a}\:\mathrm{row} \\ $$$$\mathrm{on}\:\mathrm{a}\:\mathrm{chair},\:\mathrm{if}\:\mathrm{their}\:\mathrm{are}, \\ $$$$\left(\mathrm{a}\right)\:\:\:\mathrm{7}\:\:\mathrm{chairs}\:\:\:\:\:\:\:\left(\mathrm{b}\right)\:\:\:\:\mathrm{3}\:\:\mathrm{chairs}\:\:\:\:\:\:\:\:\mathrm{available} \\ $$

Question Number 110154    Answers: 0   Comments: 0

prove that ∫_0 ^1 ∫_0 ^1 ((tanh^(−1) (^4 (√x))tanh^(−1) (^4 (√y)))/(x(√y)))=π^2

$${prove}\:{that}\: \\ $$$$\int_{\mathrm{0}} ^{\mathrm{1}} \int_{\mathrm{0}} ^{\mathrm{1}} \frac{\mathrm{tanh}^{−\mathrm{1}} \left(^{\mathrm{4}} \sqrt{{x}}\right)\mathrm{tanh}^{−\mathrm{1}} \left(^{\mathrm{4}} \sqrt{{y}}\right)}{{x}\sqrt{{y}}}=\pi^{\mathrm{2}} \\ $$

Question Number 110149    Answers: 0   Comments: 1

find the domain f(x,y)=x+4(√(y )) ?

$${find}\:{the}\:{domain}\:{f}\left({x},{y}\right)={x}+\mathrm{4}\sqrt{{y}\:}\:? \\ $$

Question Number 110145    Answers: 2   Comments: 0

prove that ∫_1 ^∞ ((ln(x))/(1+x+x^2 +x^3 ))dx=(G/2)−(π^2 /(32)) G(catalan constant)

$${prove}\:{that} \\ $$$$\int_{\mathrm{1}} ^{\infty} \frac{\mathrm{ln}\left({x}\right)}{\mathrm{1}+{x}+{x}^{\mathrm{2}} +{x}^{\mathrm{3}} }{dx}=\frac{{G}}{\mathrm{2}}−\frac{\pi^{\mathrm{2}} }{\mathrm{32}} \\ $$$${G}\left({catalan}\:{constant}\right) \\ $$

Question Number 110143    Answers: 2   Comments: 0

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