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CBSE Class 11 Maths Notes Chapter 13: In CBSE Class 11 Maths, Chapter 13 is all about Limits and Derivatives. These are important ideas in calculus, a branch of math used in many fields. In this chapter, students learn about limits, which show how values get closer to each other.
They also study derivatives, which help find rates of change and slopes of curves. By understanding these concepts, students can solve problems in math, science, and engineering. The notes for this chapter explain these ideas clearly, with examples to help students learn and practice. Mastering limits and derivatives in this chapter sets a strong foundation for future math studies and real-world applications.CBSE Class 11 Maths Notes Chapter 13 PDF
Theorem 1 states various properties of limits for two functions 𝑓 f and 𝑔 g :
If both lim𝑥→𝑎𝑓(𝑥) lim x → a f ( x ) and lim𝑥→𝑎𝑔(𝑥) lim x → a g ( x ) exist, then:We know that
Hence,
Let
be a polynomial function
= lim x → a a 0 + lim x → a a 1 x + lim x → a a 2 x 2 + . . . + lim x → a a n x n =lim𝑥→𝑎𝑎0+lim𝑥→𝑎𝑎1𝑥+lim𝑥→𝑎𝑎2𝑥2+...+lim𝑥→𝑎𝑎𝑛𝑥𝑛
= a 0 + a 1 lim x → a x + a 2 lim x → a x 2 + . . . + a n lim x → a x n =𝑎0+𝑎1lim𝑥→𝑎𝑥+𝑎2lim𝑥→𝑎𝑥2+...+𝑎𝑛lim𝑥→𝑎𝑥𝑛
= f ( a ) =𝑓(𝑎)
A rational function 𝑓 f is one where 𝑓(𝑥)=𝑔(𝑥)ℎ(𝑥) f ( x ) = h ( x ) g ( x ) , and 𝑔(𝑥) g ( x ) and ℎ(𝑥) h ( x ) are polynomials such that ℎ(𝑥)≠0 h ( x ) = 0 . Then, lim𝑥→𝑎𝑓(𝑥)=lim𝑥→𝑎𝑔(𝑥)ℎ(𝑥)=lim𝑥→𝑎𝑔(𝑥)lim𝑥→𝑎ℎ(𝑥)=𝑔(𝑎)ℎ(𝑎) lim x → a f ( x ) = lim x → a h ( x ) g ( x ) = l i m x → a h ( x ) l i m x → a g ( x ) = h ( a ) g ( a ) However, if ℎ(𝑎)=0 h ( a ) = 0 , there are two scenarios:Theorem 2
For any positive integer n 𝑛 , lim x → a x n − a n x − a = n a n − 1 lim𝑥→𝑎𝑥𝑛−𝑎𝑛𝑥−𝑎=𝑛𝑎𝑛−1 .
The proof is shown below.
Dividing ( x n − a n ) (𝑥𝑛−𝑎𝑛) by ( x − a ) (𝑥−𝑎) ,
lim x → a x n − a n x − a = lim x → a ( x n − 1 + x n − 2 a + x n − 3 a 2 + . . . + x a n − 2 + a n − 1 ) lim𝑥→𝑎𝑥𝑛−𝑎𝑛𝑥−𝑎=lim𝑥→𝑎(𝑥𝑛−1+𝑥𝑛−2𝑎+𝑥𝑛−3𝑎2+...+𝑥𝑎𝑛−2+𝑎𝑛−1)
= a n − 1 + a a n − 2 + . . . + a n − 2 ( a ) + a n − 1 =𝑎𝑛−1+𝑎𝑎𝑛−2+...+𝑎𝑛−2(𝑎)+𝑎𝑛−1
= a n − 1 + a n − 1 + . . . + a n − 1 + a n − 1 ( n terms ) =𝑎𝑛−1+𝑎𝑛−1+...+𝑎𝑛−1+𝑎𝑛−1(𝑛 terms)
= n a n − 1 =𝑛𝑎𝑛−1
Theorem 3
Theorem 4
Theorem 6
Theorem 6 states that the derivative of a function 𝑓(𝑥)=𝑥𝑛 f ( x ) = x n is 𝑛𝑥𝑛−1 n x n − 1 for any positive integer 𝑛 n . Proof: By the definition of the derivative function, we have: 𝑓′(𝑥)=limℎ→0(𝑥+ℎ)𝑛−𝑥𝑛ℎ=limℎ→0ℎ(𝑛𝑥𝑛−1+…+ℎ𝑛−1)ℎ f ′ ( x ) = lim h → 0 h ( x + h ) n − x n = lim h → 0 h h ( n x n − 1 + … + h n − 1 ) =limℎ→0(𝑛𝑥𝑛−1+…+ℎ𝑛−1)=𝑛𝑥𝑛−1 = lim h → 0 ( n x n − 1 + … + h n − 1 ) = n x n − 1 This can also be proved alternatively: 𝑑𝑑𝑥(𝑥𝑛)=𝑑𝑑𝑥(𝑥⋅𝑥𝑛−1) d x d ( x n ) = d x d ( x ⋅ x n − 1 ) =𝑑𝑑𝑥(𝑥)⋅(𝑥𝑛−1)+𝑥⋅𝑑𝑑𝑥(𝑥𝑛−1) = d x d ( x ) ⋅ ( x n − 1 ) + x ⋅ d x d ( x n − 1 ) (By the product rule) =1⋅𝑥𝑛−1+𝑥⋅((𝑛−1)𝑥𝑛−2) = 1 ⋅ x n − 1 + x ⋅ (( n − 1 ) x n − 2 ) (By induction hypothesis) =𝑥𝑛−1+(𝑛−1)𝑥𝑛−1=𝑛𝑥𝑛−1 = x n − 1 + ( n − 1 ) x n − 1 = n x n − 1Complete Syllabus : The notes cover all the topics in Chapter 13 as per the CBSE syllabus, ensuring that students don't miss any important concepts.
Key Concepts : They provide a concise and clear explanation of key concepts such as limits, continuity, and derivatives, which are fundamental to understanding calculus.
Easy to Understand : The notes break down complex topics into simpler terms, making it easier for students to grasp difficult concepts..
Self-Study : With comprehensive notes, students can study on their own without much dependence on external help, boosting their confidence.
Concept Clarity : Clear understanding of fundamental concepts helps in building a strong foundation for higher studies.