Mister Exam

Graphing y = cot2x

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The graph:

from to

Intersection points:

does show?

Piecewise:

The solution

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f(x) = cot(2*x)
f(x)=cot(2x)f{\left(x \right)} = \cot{\left(2 x \right)}
f = cot(2*x)
The graph of the function
0-60-50-40-30-20-101020304050-500500
The points of intersection with the X-axis coordinate
Graph of the function intersects the axis X at f = 0
so we need to solve the equation:
cot(2x)=0\cot{\left(2 x \right)} = 0
Solve this equation
The points of intersection with the axis X:

Analytical solution
x1=π4x_{1} = \frac{\pi}{4}
Numerical solution
x1=63.6172512351933x_{1} = -63.6172512351933
x2=52.621676947629x_{2} = 52.621676947629
x3=11.7809724509617x_{3} = -11.7809724509617
x4=80.8960108299372x_{4} = 80.8960108299372
x5=74.6128255227576x_{5} = -74.6128255227576
x6=58.9048622548086x_{6} = 58.9048622548086
x7=66.7588438887831x_{7} = 66.7588438887831
x8=90.3207887907066x_{8} = 90.3207887907066
x9=63.6172512351933x_{9} = 63.6172512351933
x10=79.3252145031423x_{10} = -79.3252145031423
x11=30.6305283725005x_{11} = 30.6305283725005
x12=18.0641577581413x_{12} = 18.0641577581413
x13=68.329640215578x_{13} = -68.329640215578
x14=60.4756585816035x_{14} = 60.4756585816035
x15=38.484510006475x_{15} = 38.484510006475
x16=11.7809724509617x_{16} = 11.7809724509617
x17=2.35619449019234x_{17} = -2.35619449019234
x18=30.6305283725005x_{18} = -30.6305283725005
x19=13.3517687777566x_{19} = -13.3517687777566
x20=90.3207887907066x_{20} = -90.3207887907066
x21=74.6128255227576x_{21} = 74.6128255227576
x22=36.9137136796801x_{22} = 36.9137136796801
x23=62.0464549083984x_{23} = -62.0464549083984
x24=91.8915851175014x_{24} = 91.8915851175014
x25=5.49778714378214x_{25} = -5.49778714378214
x26=27.4889357189107x_{26} = -27.4889357189107
x27=96.6039740978861x_{27} = -96.6039740978861
x28=10.2101761241668x_{28} = -10.2101761241668
x29=62.0464549083984x_{29} = 62.0464549083984
x30=40.0553063332699x_{30} = 40.0553063332699
x31=25.9181393921158x_{31} = 25.9181393921158
x32=68.329640215578x_{32} = 68.329640215578
x33=85.6083998103219x_{33} = 85.6083998103219
x34=2.35619449019234x_{34} = 2.35619449019234
x35=69.9004365423729x_{35} = -69.9004365423729
x36=84.037603483527x_{36} = 84.037603483527
x37=3.92699081698724x_{37} = -3.92699081698724
x38=46.3384916404494x_{38} = 46.3384916404494
x39=99.7455667514759x_{39} = -99.7455667514759
x40=44.7676953136546x_{40} = 44.7676953136546
x41=91.8915851175014x_{41} = -91.8915851175014
x42=33.7721210260903x_{42} = -33.7721210260903
x43=25.9181393921158x_{43} = -25.9181393921158
x44=38.484510006475x_{44} = -38.484510006475
x45=22.776546738526x_{45} = 22.776546738526
x46=35.3429173528852x_{46} = -35.3429173528852
x47=5.49778714378214x_{47} = 5.49778714378214
x48=43.1968989868597x_{48} = -43.1968989868597
x49=24.3473430653209x_{49} = -24.3473430653209
x50=27.4889357189107x_{50} = 27.4889357189107
x51=8.63937979737193x_{51} = 8.63937979737193
x52=3.92699081698724x_{52} = 3.92699081698724
x53=47.9092879672443x_{53} = -47.9092879672443
x54=54.1924732744239x_{54} = -54.1924732744239
x55=84.037603483527x_{55} = -84.037603483527
x56=41.6261026600648x_{56} = 41.6261026600648
x57=99.7455667514759x_{57} = 99.7455667514759
x58=85.6083998103219x_{58} = -85.6083998103219
x59=21.2057504117311x_{59} = -21.2057504117311
x60=52.621676947629x_{60} = -52.621676947629
x61=32.2013246992954x_{61} = -32.2013246992954
x62=60.4756585816035x_{62} = -60.4756585816035
x63=57.3340659280137x_{63} = -57.3340659280137
x64=54.1924732744239x_{64} = 54.1924732744239
x65=65.1880475619882x_{65} = -65.1880475619882
x66=87.1791961371168x_{66} = -87.1791961371168
x67=55.7632696012188x_{67} = -55.7632696012188
x68=7.06858347057703x_{68} = -7.06858347057703
x69=69.9004365423729x_{69} = 69.9004365423729
x70=96.6039740978861x_{70} = 96.6039740978861
x71=10.2101761241668x_{71} = 10.2101761241668
x72=16.4933614313464x_{72} = -16.4933614313464
x73=33.7721210260903x_{73} = 33.7721210260903
x74=93.4623814442964x_{74} = 93.4623814442964
x75=46.3384916404494x_{75} = -46.3384916404494
x76=93.4623814442964x_{76} = -93.4623814442964
x77=16.4933614313464x_{77} = 16.4933614313464
x78=24.3473430653209x_{78} = 24.3473430653209
x79=77.7544181763474x_{79} = -77.7544181763474
x80=18.0641577581413x_{80} = -18.0641577581413
x81=98.174770424681x_{81} = 98.174770424681
x82=88.7499924639117x_{82} = 88.7499924639117
x83=82.4668071567321x_{83} = -82.4668071567321
x84=82.4668071567321x_{84} = 82.4668071567321
x85=14.9225651045515x_{85} = 14.9225651045515
x86=19.6349540849362x_{86} = 19.6349540849362
x87=98.174770424681x_{87} = -98.174770424681
x88=71.4712328691678x_{88} = 71.4712328691678
x89=49.4800842940392x_{89} = -49.4800842940392
x90=19.6349540849362x_{90} = -19.6349540849362
x91=76.1836218495525x_{91} = 76.1836218495525
x92=55.7632696012188x_{92} = 55.7632696012188
x93=71.4712328691678x_{93} = -71.4712328691678
x94=76.1836218495525x_{94} = -76.1836218495525
x95=40.0553063332699x_{95} = -40.0553063332699
x96=49.4800842940392x_{96} = 49.4800842940392
x97=47.9092879672443x_{97} = 47.9092879672443
x98=77.7544181763474x_{98} = 77.7544181763474
x99=41.6261026600648x_{99} = -41.6261026600648
x100=32.2013246992954x_{100} = 32.2013246992954
The points of intersection with the Y axis coordinate
The graph crosses Y axis when x equals 0:
substitute x = 0 to cot(2*x).
~\tilde{\infty}
The result:
f(0)=~f{\left(0 \right)} = \tilde{\infty}
sof doesn't intersect Y
Extrema of the function
In order to find the extrema, we need to solve the equation
ddxf(x)=0\frac{d}{d x} f{\left(x \right)} = 0
(the derivative equals zero),
and the roots of this equation are the extrema of this function:
ddxf(x)=\frac{d}{d x} f{\left(x \right)} =
the first derivative
2cot2(2x)2=0- 2 \cot^{2}{\left(2 x \right)} - 2 = 0
Solve this equation
Solutions are not found,
function may have no extrema
Inflection points
Let's find the inflection points, we'll need to solve the equation for this
d2dx2f(x)=0\frac{d^{2}}{d x^{2}} f{\left(x \right)} = 0
(the second derivative equals zero),
the roots of this equation will be the inflection points for the specified function graph:
d2dx2f(x)=\frac{d^{2}}{d x^{2}} f{\left(x \right)} =
the second derivative
8(cot2(2x)+1)cot(2x)=08 \left(\cot^{2}{\left(2 x \right)} + 1\right) \cot{\left(2 x \right)} = 0
Solve this equation
The roots of this equation
x1=π4x_{1} = \frac{\pi}{4}

Сonvexity and concavity intervals:
Let’s find the intervals where the function is convex or concave, for this look at the behaviour of the function at the inflection points:
Concave at the intervals
(,π4]\left(-\infty, \frac{\pi}{4}\right]
Convex at the intervals
[π4,)\left[\frac{\pi}{4}, \infty\right)
Horizontal asymptotes
Let’s find horizontal asymptotes with help of the limits of this function at x->+oo and x->-oo
limxcot(2x)=,\lim_{x \to -\infty} \cot{\left(2 x \right)} = \left\langle -\infty, \infty\right\rangle
Let's take the limit
so,
equation of the horizontal asymptote on the left:
y=,y = \left\langle -\infty, \infty\right\rangle
limxcot(2x)=,\lim_{x \to \infty} \cot{\left(2 x \right)} = \left\langle -\infty, \infty\right\rangle
Let's take the limit
so,
equation of the horizontal asymptote on the right:
y=,y = \left\langle -\infty, \infty\right\rangle
Inclined asymptotes
Inclined asymptote can be found by calculating the limit of cot(2*x), divided by x at x->+oo and x ->-oo
limx(cot(2x)x)=limx(cot(2x)x)\lim_{x \to -\infty}\left(\frac{\cot{\left(2 x \right)}}{x}\right) = \lim_{x \to -\infty}\left(\frac{\cot{\left(2 x \right)}}{x}\right)
Let's take the limit
so,
inclined asymptote equation on the left:
y=xlimx(cot(2x)x)y = x \lim_{x \to -\infty}\left(\frac{\cot{\left(2 x \right)}}{x}\right)
limx(cot(2x)x)=limx(cot(2x)x)\lim_{x \to \infty}\left(\frac{\cot{\left(2 x \right)}}{x}\right) = \lim_{x \to \infty}\left(\frac{\cot{\left(2 x \right)}}{x}\right)
Let's take the limit
so,
inclined asymptote equation on the right:
y=xlimx(cot(2x)x)y = x \lim_{x \to \infty}\left(\frac{\cot{\left(2 x \right)}}{x}\right)
Even and odd functions
Let's check, whether the function even or odd by using relations f = f(-x) и f = -f(-x).
So, check:
cot(2x)=cot(2x)\cot{\left(2 x \right)} = - \cot{\left(2 x \right)}
- No
cot(2x)=cot(2x)\cot{\left(2 x \right)} = \cot{\left(2 x \right)}
- Yes
so, the function
is
odd
The graph
Graphing y = cot2x