Continuity — Class 11 Maharashtra HSC Mathematics revision notes
A 4-page visual revision sheet for Continuity, written for Class 11 Maharashtra HSC Mathematics. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.
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Continuity in one look
drawn without lifting the pen: three conditions, and dropping any one breaks it
Continuity at a point x=a
condition 1: f is defined at a, and on an open interval around itf(a)
condition 2: the limit as x approaches a existslim_xto af(x)
condition 3: that limit equals the function's own value at alim_xto af(x)=f(a)
Continuity from the left and from the right
f is continuous from the right at a if lim_xto a^+f(x)=f(a)
f is continuous from the left at a if lim_xto a^-f(x)=f(a)
continuous from both sides at a is exactly continuous at a
continuity over an interval: continuous at every interior point
plus right-continuous at a closed left endpoint
and left-continuous at a closed right endpoint
Worked: continuity of a three-piece function
Q. f(x)=3x+1 for x<2, =7 for 2≤ x<4, =x^2-8 for x≥4. Test continuity at x=2 and x=4
at x=2: f(2)=7. LHL=lim_xto2^-(3x+1)=3(2)+1=7. RHL=lim_xto2^+(7)=7
LHL=RHL=f(2)=7, so f is continuous at x=2
at x=4: f(4)=4^2-8=8. LHL=lim_xto4^-(7)=7. RHL=lim_xto4^+(x^2-8)=4^2-8=8
LHL=7 but RHL=8, so lim_xto4f(x) does not exist
Answer: continuous at x=2, discontinuous at x=4 (a jump discontinuity)
Functions that are always continuous
constant and power functions: f(x)=k and f(x)=x^n are continuous on all of R
every polynomial: built from sums and products of continuous pieces, so it stays continuous
sin x and cos x: continuous at every real x, no exceptions
exponential and logarithm: a^x continuous on R, log_bx continuous on (0,∞)
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What this Continuity sheet covers
Continuity at a point x=a
condition 1: f is defined at a, and on an open interval around it
condition 2: the limit as x approaches a exists
condition 3: that limit equals the function's own value at a
What an unbroken curve looks like
Continuity from the left and from the right
Worked: continuity of a three-piece function
Functions that are always continuous
constant and power functions
every polynomial
sin x and cos x
exponential and logarithm
Properties of continuous functions
Three ways continuity fails at x=a
Worked: identifying a removable discontinuity
Worked: identifying a jump discontinuity
The Intermediate Value Theorem
Worked: locating a root with the Intermediate Value Theorem
These notes are not a standalone PDF. CapCompass plans Mathematics chapter by chapter against your real exam dates and free hours, and when the plan reaches Continuity the sheet opens inside the study block itself — at the page covering the sub-topic that block is on, with the timer still running. Revision arrives at the moment the plan says revise, instead of having to be gone looking for.