- •Донецьк 2006
- •Integral calculus lecture no. 19. Primitive and indefinite integral
- •Point 1. Primitive
- •Properties of primitives
- •Point 2. Indefinite integral and its properties
- •Point 3. Integration by substitution (change of a variable)
- •Point 4. Integration by parts
- •Lecture no.20. Classes of integrable functions
- •Point 1. Rational functions (rational fractions)
- •Point 2. Trigonometric functions
- •Universal trigonometrical substitution
- •Other substitutions
- •Point 3. Irrational functions
- •Quadratic irrationalities. Trigonometric substitutions
- •Quadratic irrationalities (general case)
- •Indefinite integral: Basic Terminology
- •Lecture no. 21. Definite integral
- •Point 1. Problems leading to the concept ofa definite integral
- •Point 2. Definite integral
- •Point 3. Properties of a definite integral
- •I ntegration of inequalities
- •Point 4. Definite integral as a function of its upper variable limit
- •Point 5. Newton-leibniz formula
- •Point 6. Main methods of evaluation a definite integral Change of a variable (substitution method)
- •Integration by parts
- •Lecture no.22. Applications of definite integral
- •Point 1. Problem – solving schemes. Areas
- •Additional remarks about the areas of plane figures
- •Point 2. Arс length
- •Point 3. Volumes
- •Volume of a body with known areas of its parallel cross-sections
- •Volume of a body of rotation
- •Point 4. Economic applications
- •Lecture no. 23. Definite integral: additional questions
- •Point 1. Approximate integration
- •Rectangular Formulas
- •Trapezium Formula
- •Simpson10 formula (parabolic formula)
- •Point 2. Improper integrals
- •Improper integrals of the first kind
- •Improper integrals of the second kind
- •Convergence tests
- •Point 3. Euler г- function
- •Definite integral: Basic Terminology
- •Lecture no. 24. Double integral
- •Point 1. Double integral
- •Point 2. Evaluation of a double integral in cartesian coordinates
- •Point 3. Improper double integrals. Poisson formula
- •Point 4. Double integral in polar coordinates
- •Double integral: Basic Terminology
- •Differential equations lecture no.25. First and second order differential equations
- •Point 1. General notions
- •Point 2. Integrable types of the first order differential equations (of de - 1)
- •1. Separated de-1 (de-1 with separated variables)
- •2. Separable de-1 (de-1 with separable variables)
- •3. Homogeneous de-1
- •4. Linear de-1
- •5. Bernoulli de-1
- •Point 3. Order reducing second order differential equations
- •Lecture no.26. Second order linear differential equations
- •Point 1. General notions
- •Point 2. Linear dependence and independence
- •Point 3. Homogeneous equations Structure of the general solution of so lhde
- •So lhde with constant coefficients
- •Point 4. Nonhomogeneous equations Structure of the general solution of so lnde
- •Method of variation of arbitrary constants
- •Method of undetermined coefficients for so lnde with constant coefficients
- •Lecture no. 27. Systems of differential equations. Approximate integration of differential equations
- •Point 1. Normal systems of differential equations
- •Point 2. Approximate integration of differential equations Successive approximations method
- •Euler method
- •Differential equations: Basic Terminology
- •Bibliography textbooks
- •Problem books
- •Contents
Point 2. Definite integral
Def. 2. Let a function be given on a segment a, b (fig. 2).
1. We divide the segment into n parts (subintervals)
by points (division points)
;
let
,
.
2. We take an arbitrary point in every subinterval find the Fig. 2 value of the function at this point and multiply this value by the length of the subinterval.
3. Adding all these products we get a sum (Cauchy1-Riemann2 integral sum)
. ( 8 )
4. If there exists the limit of the integral sum (8) as , this limit is called the definite integral of the function over the segment a, b and is denoted
. ( 9 )
We read the left side of (9) as “definite integral from a to b of ”.
have the same names as for indefinite integral; a is called the lower limit of integration, b the upper limit of integration.
Def. 3. A function is called integrable on [over] the segment a, b, if its definite integral (9) exists.
Theorem 1 (existence theorem). If a function is continuous one on the segment a, b then it is integrable over this segment.
Geometric sense of a definite integral. If a function is non-negative, , then by (2), (3) its definite integral is the area of a curvilinear trapezium (1), fig. 1,
( 10 )
Economical sense of a definite integral. If a function is a labour producti-vity of some factory, then its produced quantity U during a time interval 0, T by vir-tue of (4), (5) is represented by a definite integral,
. ( 11 )
Physical sense of a definite integral. If a function is the velocity of a material point then, on the base of (6), (7), the length path L traveled by the point during a time interval from t = 0 to t = T is given by a definite integral
( 12 )
Ex. 1. Prove that
( 13 )
■The integrand , and so the integral sum (8) equals the length of the segment , that is
,
therefore its limit, which is the integral (13), equals .■
Note 1. Definite integral doesn’t depend on a variable of integration. It means that
( 14 )
Def. 4 (definite integral with equal limits of integration).
( 15 )
Def. 5 (interchanging limits of integration).
( 16 )
Point 3. Properties of a definite integral
1 (homogeneity). A constant factor k can by taken outside the integral sign,
.
■Integral sums for the left and right sides are equal, because of
,
therefore their limits are also equal.■
2 (additivity with respect to an integrand). If be two integrable functions then
.
Prove this property yourselves.
Corollary (linearity). For any two integrable functions and arbitrary constants
.
3 (additivity with respect to an interval of integration). For any a, b, c
if all three integrals exist.
■1) Let at first c(a, b). We form an integral sum such that c be a division point. In this case (notations are clear)
,
and the passage to limit as gives the property in question.
2) Let now a disposition of points a, b, c is arbitrary, for example a < b < c. Using the first case and the definitions 4, 5 we’ll have
.■