Graphs without calculus.

1.How do curves of following differ(if they)
a) y=log3x2 and y=2log3x
b) y=2log2x and y=x
c) y=tanx.cotx and y=1

2.Sketch the curves of following without help of calculus............
(draw the rough sketch and post it otherwise make it urself and match it with soln.after few days.)

a) y=1/(log1/2sinx)
b) logxlogyx>0
c) cosx-cosy>0
d) log|sinx|y>0

21 Answers

1
Shalini Kumari ·

my dirty graph for this question [3]

33
Abhishek Priyam ·

Not clicking anything

Well may be after AITS part test 2 it will click
:P

33
Abhishek Priyam ·

[7]

[1]

1
Grandmaster ·

plz sketch th curve cosec2x-sec2y<xy

33
Abhishek Priyam ·

@Shailesh, no shailesh i'm a student of class 12 preparing....

That y=1/(log1/2sinx) is gr8 try it....

33
Abhishek Priyam ·

wait those vertical lines not in curve is of kpi/2 as sinx≠o or ±1

33
Abhishek Priyam ·

that log|sinx|y>0 i think is correct

33
Abhishek Priyam ·

that logxlogyx>0 question u solved absolutily correct....
Case 1: x>1

logyx>1 so logx/logy>1 so 1<y<x will be solution.

Case 2: x<1

logyx<1 so logx/logy<1 so 0<y<x will be solution.

____________________________________________________

but graph u drew in hadbadi so only sketching is wrong for x>1

pt(1,1)is also not in graph...

33
Abhishek Priyam ·

Cosx-cosy>0

u drew grayed parts as part of graph....
so (pi/2,0)is part of graph but cos(pi/2)-cos(0)<0

tills sq part that is graphs will be square it is correct but slightly displaced squares think again.
write the given inequality as products of sin terms....

11
Shailesh ·

in this image all white lines are not included in the graph. Also Y axis is not include. Also the gray part is only till Y=0 to Y=1

This is the solution for part d...

Abhishek tell me if it is right or wrong?

11
Shailesh ·

d) log|sinx|y>0

lny/ ln|sinx|

for this part, denominator is always negative. or undefined at x=2npi

so y has to be less than 1.

So the function will be like rectangles.

33
Abhishek Priyam ·

For ex curve of y=21/x

first domain of fn. is all real x except x≠0.

for x>0,
if x increase without bound 1/x decreases to 0 and 21/x decreases to 1.

for x=o+ i/x is infinitely large so 21/x → ∞
so for x>0 21/x decreases exponentially from ∞ to 1.

for x=0- 1/x is infinitely large negative. now 2-∞=0.
also for x<0, 21/x is similar top curve 1/21/x for x>0.
when x→-∞, 1/x→0- so 21/x→1-

Similar inspection for drawing curves is very useful for quick graph sketching if u practice it and get control over it.

1
Shalini Kumari ·

logxlogyx>0

since x and y are used in base so x,y>0

Case 1: x>1

logyx>1 so logx/logy>1 so 1<y<x will be solution.

Case 2: x<1

logyx<1 so logx/logy<1 so 0<y<x will be solution.

11
Shailesh ·

now back to this question. I find this one very good.. let me think and draw the graph [1]

Repeat this gray area everywhere.. I think this is the graph of the functions given!

11
Shailesh ·

2 c) cosx-cosy>0

I think it will be lot of squares of side 2pi repeated ...

If i can draw one square from (-pi,-pi) to (pi,pi) then we can just keep repeating this square everywhere.. because it is periodic

11
Shailesh ·

Abhishek are u administrator here on this site?

11
Shailesh ·

c) y=tanx.cotx and y=1
slightly different but same difference again.. it has different domain

points n.pi/2 are not defined.

So in a, b, c the both functions have different domains.. That is the difference

11
Shailesh ·

b) y=2log2x and y=x

Again same difference. for -ve x it is not defined.

11
Shailesh ·

1 a ) 1.How do curves of following differ(if they)
a) y=log3x2 and y=2log3x

The first graph will be symmetric about x axis.. and defined for -ve x.

The 2nd graph is not symmetric and not defined for -ve x

1
Kumar Saurabh ·

good explanation abhishek :)

thanks

33
Abhishek Priyam ·

One guess for sketching......

almost in every cases of basic log or exponential or similar nature curves......

these are common whenever there is 1/x type involved. Notice the point of infleections here this is also true for previous curve y=21/x for x=0-

But this is not a full proof method of finding pts of inflections but calculus may help.

This graphing technique is helpful for solving problems related to no of solns, limits and many more but not involving graph minute details.

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