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Question Number 227673    Answers: 1   Comments: 0

Question Number 227670    Answers: 0   Comments: 1

Question Number 227667    Answers: 1   Comments: 0

sin7xcos5x−cos7xsin5x = (1/2) x = ?

$$\mathrm{sin7xcos5x}−\mathrm{cos7xsin5x}\:=\:\frac{\mathrm{1}}{\mathrm{2}} \\ $$$$\mathrm{x}\:=\:? \\ $$

Question Number 227656    Answers: 1   Comments: 0

Question Number 227652    Answers: 2   Comments: 0

if (a/(y+z))=(b/(z+x))=(c/(x+y)) prove ((a(b−c))/(y^2 −z^2 ))=((b(c−a))/(z^2 −x^2 ))=((c(a−b))/(x^2 −y^2 ))

$${if} \\ $$$$\frac{{a}}{{y}+{z}}=\frac{{b}}{{z}+{x}}=\frac{{c}}{{x}+{y}}\: \\ $$$${prove} \\ $$$$\frac{{a}\left({b}−{c}\right)}{{y}^{\mathrm{2}} −{z}^{\mathrm{2}} }=\frac{{b}\left({c}−{a}\right)}{{z}^{\mathrm{2}} −{x}^{\mathrm{2}} }=\frac{{c}\left({a}−{b}\right)}{{x}^{\mathrm{2}} −{y}^{\mathrm{2}} } \\ $$

Question Number 227651    Answers: 1   Comments: 0

log_5 x = 25 x = ?

$$\mathrm{log}_{\mathrm{5}} \:\mathrm{x}\:=\:\mathrm{25} \\ $$$$\mathrm{x}\:=\:? \\ $$

Question Number 227649    Answers: 1   Comments: 0

25^(log_5 (√2) + 1) = ?

$$\mathrm{25}^{\boldsymbol{\mathrm{log}}_{\mathrm{5}} \:\sqrt{\mathrm{2}}\:+\:\mathrm{1}} \:\:\:=\:\:\:? \\ $$

Question Number 227635    Answers: 0   Comments: 0

prove: 8Σ_(n=0) ^∞ (1/((2n−1)sinh((2n−1)π)))=ln2

$$\:\:\:\:\:\:\:\:\:\:\:\:\:\mathrm{prove}:\:\mathrm{8}\underset{{n}=\mathrm{0}} {\overset{\infty} {\sum}}\frac{\mathrm{1}}{\left(\mathrm{2}{n}−\mathrm{1}\right)\mathrm{sinh}\left(\left(\mathrm{2}{n}−\mathrm{1}\right)\pi\right)}=\mathrm{ln2} \\ $$

Question Number 227634    Answers: 0   Comments: 0

prove: p>1,n≥2 (1/n^p )<(1/(p−1))∙[(1/((n−1)^(p− 1) ))−(1/n^(p−1) )]

$$\mathrm{prove}:\:\:\:\:\:\:\:\:\:{p}>\mathrm{1},{n}\geqslant\mathrm{2} \\ $$$$\:\:\:\:\:\:\:\:\:\:\frac{\mathrm{1}}{{n}^{{p}} }<\frac{\mathrm{1}}{{p}−\mathrm{1}}\centerdot\left[\frac{\mathrm{1}}{\left({n}−\mathrm{1}\right)^{{p}−\:\mathrm{1}} }−\frac{\mathrm{1}}{{n}^{{p}−\mathrm{1}} }\right] \\ $$

Question Number 227633    Answers: 1   Comments: 0

(3/(log_2 23!)) + (3/(log_3 23!)) + (3/(log_4 23!)) +...+ (3/(log_(22) 23!)) + (3/(log_(23) 23!)) = ?

$$\frac{\mathrm{3}}{\mathrm{log}_{\mathrm{2}} \mathrm{23}!}\:+\:\frac{\mathrm{3}}{\mathrm{log}_{\mathrm{3}} \mathrm{23}!}\:+\:\frac{\mathrm{3}}{\mathrm{log}_{\mathrm{4}} \mathrm{23}!}\:+...+\:\frac{\mathrm{3}}{\mathrm{log}_{\mathrm{22}} \mathrm{23}!}\:+\:\frac{\mathrm{3}}{\mathrm{log}_{\mathrm{23}} \mathrm{23}!}\:=\:? \\ $$

Question Number 227632    Answers: 1   Comments: 0

If 4a^2 + 9b^2 = 13ab Find ((2lg(2a + 3b)−lg25)/(5lg(ab))) = ?

$$\mathrm{If}\:\:\:\mathrm{4a}^{\mathrm{2}} \:+\:\mathrm{9b}^{\mathrm{2}} \:=\:\mathrm{13ab} \\ $$$$\mathrm{Find}\:\:\:\frac{\mathrm{2}\boldsymbol{\mathrm{lg}}\left(\mathrm{2a}\:+\:\mathrm{3b}\right)−\boldsymbol{\mathrm{lg}}\mathrm{25}}{\mathrm{5}\boldsymbol{\mathrm{lg}}\left(\mathrm{ab}\right)}\:=\:? \\ $$

Question Number 227629    Answers: 1   Comments: 0

Let the equations on x (a,b,c∈R; a≠0) ax^2 +bx+c=0 w/ roots r and s and, x^2 +bx+ac=0 w/ roots m and n Prove that: r=(m/a) and s=(n/a)

$${Let}\:{the}\:{equations}\:{on}\:{x}\:\left({a},{b},{c}\in\mathbb{R};\:{a}\neq\mathrm{0}\right) \\ $$$${ax}^{\mathrm{2}} +{bx}+{c}=\mathrm{0}\:{w}/\:{roots}\:{r}\:{and}\:{s} \\ $$$$\:{and},\:{x}^{\mathrm{2}} +{bx}+{ac}=\mathrm{0}\:{w}/\:{roots}\:{m}\:{and}\:{n} \\ $$$${Prove}\:{that}:\:{r}=\frac{{m}}{{a}}\:{and}\:{s}=\frac{{n}}{{a}} \\ $$

Question Number 227612    Answers: 0   Comments: 0

m_− R (R/m_− ) ⇔

$$ \\ $$$$\:\:\:\:\underset{−} {{m}}\: {R} \\ $$$$\:\:\:\:\:\:\: \:\:\frac{{R}}{\underset{−} {{m}}}\:\:\:\:\Leftrightarrow \: \\ $$

Question Number 227605    Answers: 0   Comments: 3

the two roots of eq x^2 +2ax−2b^2 =0 are α&β a,b are rational but a^2 +b^2 is not complete square. make a quad eq whose one root is α+β+(√(α^2 +β^2 ))

$${the}\:{two}\:{roots}\:{of}\:{eq}\:{x}^{\mathrm{2}} +\mathrm{2}{ax}−\mathrm{2}{b}^{\mathrm{2}} =\mathrm{0}\:{are} \\ $$$$\alpha\&\beta \\ $$$${a},{b}\:{are}\:{rational}\:{but}\:{a}^{\mathrm{2}} +{b}^{\mathrm{2}} \:{is}\:{not}\:{complete} \\ $$$${square}.\:{make}\:{a}\:{quad}\:{eq}\:{whose}\:{one}\:{root}\:{is}\: \\ $$$$\alpha+\beta+\sqrt{\alpha^{\mathrm{2}} +\beta^{\mathrm{2}} } \\ $$

Question Number 227607    Answers: 2   Comments: 0

Question Number 227592    Answers: 0   Comments: 8

∀ε>0,∃δ>0 s.t. ∣h∣<δ ⇒ ∣((e^(x_0 +h) −e^x_0 )/h)−e^x_0 ∣<ε... (Don′t use Taylar/Maclaurin Series, and derivation only use inequality properties Damn.....i stuck here again .. e^x_0 ∣((e^h −1)/h)−1∣<𝛆 ..... fuck ∣((e^h −1)/h)−1∣ how can i show that h+1<e^h <(1/(1−h)) , ∣h∣<1

$$\forall\epsilon>\mathrm{0},\exists\delta>\mathrm{0}\:\mathrm{s}.\mathrm{t}.\:\mid{h}\mid<\delta\:\Rightarrow\:\mid\frac{{e}^{{x}_{\mathrm{0}} +{h}} −{e}^{{x}_{\mathrm{0}} } }{{h}}−{e}^{{x}_{\mathrm{0}} } \mid<\epsilon... \\ $$$$\left(\mathrm{Don}'\mathrm{t}\:\mathrm{use}\:\mathrm{Taylar}/\mathrm{Maclaurin}\:\mathrm{Series},\:\mathrm{and}\:\mathrm{derivation}\right. \\ $$$$\mathrm{only}\:\mathrm{use}\:\mathrm{inequality}\:\mathrm{properties} \\ $$$$\mathrm{Damn}.....\mathrm{i}\:\mathrm{stuck}\:\mathrm{here}\:\mathrm{again}\:..\:\: \\ $$$${e}^{{x}_{\mathrm{0}} } \mid\frac{{e}^{{h}} −\mathrm{1}}{{h}}−\mathrm{1}\mid<\boldsymbol{\epsilon}\:\:..... \\ $$$$\mathrm{fuck}\:\mid\frac{{e}^{{h}} −\mathrm{1}}{{h}}−\mathrm{1}\mid\: \\ $$$$\mathrm{how}\:\mathrm{can}\:\mathrm{i}\:\mathrm{show}\:\mathrm{that}\:{h}+\mathrm{1}<{e}^{{h}} <\frac{\mathrm{1}}{\mathrm{1}−{h}}\:,\:\mid{h}\mid<\mathrm{1} \\ $$

Question Number 227582    Answers: 1   Comments: 0

cos^2 (((3x)/2) + ((11π)/2)) - sin^2 (((3x)/2) + ((11π)/2)) = - (1/2) x = ?

$$\mathrm{cos}^{\mathrm{2}} \left(\frac{\mathrm{3x}}{\mathrm{2}}\:+\:\frac{\mathrm{11}\pi}{\mathrm{2}}\right)\:-\:\mathrm{sin}^{\mathrm{2}} \left(\frac{\mathrm{3x}}{\mathrm{2}}\:+\:\frac{\mathrm{11}\pi}{\mathrm{2}}\right)\:=\:-\:\frac{\mathrm{1}}{\mathrm{2}} \\ $$$$\mathrm{x}\:=\:? \\ $$

Question Number 227580    Answers: 1   Comments: 0

(π/4)arctan(tan((7π)/8))+tan2x=(1/2)cos(arccos(−(1/2))+(π/3)) x = ?

$$\frac{\pi}{\mathrm{4}}\mathrm{arctan}\left(\mathrm{tan}\frac{\mathrm{7}\pi}{\mathrm{8}}\right)+\mathrm{tan2x}=\frac{\mathrm{1}}{\mathrm{2}}\mathrm{cos}\left(\mathrm{arccos}\left(−\frac{\mathrm{1}}{\mathrm{2}}\right)+\frac{\pi}{\mathrm{3}}\right) \\ $$$$\mathrm{x}\:=\:? \\ $$

Question Number 227579    Answers: 1   Comments: 0

cos6x = ((2tan(π/8))/(1−tan^2 (π/8))) ⇒ x = ?

$$\mathrm{cos6x}\:=\:\frac{\mathrm{2tan}\frac{\pi}{\mathrm{8}}}{\mathrm{1}−\mathrm{tan}^{\mathrm{2}} \frac{\pi}{\mathrm{8}}}\:\:\:\:\:\Rightarrow\:\:\:\:\mathrm{x}\:=\:? \\ $$

Question Number 227578    Answers: 1   Comments: 0

sin3x + sin^2 (π/4) = cos^2 (π/4) + ((√3)/2) x = ?

$$\mathrm{sin3x}\:+\:\mathrm{sin}^{\mathrm{2}} \frac{\pi}{\mathrm{4}}\:=\:\mathrm{cos}^{\mathrm{2}} \frac{\pi}{\mathrm{4}}\:+\:\frac{\sqrt{\mathrm{3}}}{\mathrm{2}} \\ $$$$\mathrm{x}\:=\:? \\ $$

Question Number 227567    Answers: 0   Comments: 0

Question Number 227568    Answers: 1   Comments: 1

AB and AC are two plane mirrors ∠BAC=α P is a point on AB and a ray falls on AC at i=γ and after n times of reflection the ray becomes parrallel to AC find γ in terms of α & n

$${AB}\:{and}\:{AC}\:{are}\:{two}\:{plane}\:{mirrors} \\ $$$$\angle{BAC}=\alpha \\ $$$${P}\:{is}\:{a}\:{point}\:{on}\:{AB}\:{and}\:{a}\:{ray}\:{falls}\:{on}\:{AC} \\ $$$${at}\:{i}=\gamma\:{and}\:{after}\:{n}\:{times}\:{of}\:{reflection} \\ $$$${the}\:{ray}\:{becomes}\:{parrallel}\:{to}\:{AC} \\ $$$${find}\:\gamma\:{in}\:{terms}\:\:{of}\:\alpha\:\&\:{n} \\ $$

Question Number 227561    Answers: 1   Comments: 1

Question Number 227534    Answers: 0   Comments: 8

Post some of the hardests problem you think fall within thescope of high school mathp cometitions under this thread. :)

$$\mathrm{Post}\:\mathrm{some}\:\mathrm{of}\:\mathrm{the}\:\mathrm{hardests} \\ $$$$\mathrm{problem}\:\mathrm{you}\:\mathrm{think}\:\mathrm{fall}\:\mathrm{within}\: \\ $$$$\mathrm{thescope}\:\mathrm{of}\:\mathrm{high}\:\mathrm{school}\:\mathrm{mathp} \\ $$$$\mathrm{cometitions}\:\mathrm{under}\:\mathrm{this}\:\mathrm{thread}. \\ $$$$\left.:\right) \\ $$

Question Number 227533    Answers: 2   Comments: 0

Question Number 227531    Answers: 0   Comments: 0

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