Mathematics_Today_-_October_2016

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(ii) xA
xkxA

dx

2
422


∫ ++
Divide numerator and denominator by x^2
and substitute x A
x

+=t, A being positive
constant.
(iii) ax bx c
px qx r

dx

2
2

++
∫ ++
put ax^2 + bx + c = l(px^2 + qx + r) + m
d
dx()px qx r n

⎛ (^2) ++
⎝⎜

⎠⎟+^
Find l, m and n by equating coefficients of
like powers of x and then split the integral
into three integrals.
TRIGONOMETRIC INTEGRALS
To find the integral axb x
cxd x
sin cos dx
sin cos




  • ∫ +
    Put a sinx + b cosx
    = L (Denominator) +M (Derivative of denominator)
    Note : To evaluate the integration of the forms
    dx
    axb x
    dx
    ab x
    dx
    (^22) sin 2 2cos (^2) ab (^2) x
    ,
    sin
    ,
    cos
    ,
    ∫∫+++∫
    dx
    axb x
    dx
    ∫( sin +++cos ) 222 ∫absin xccosx
    and
    Step 1 : Divide by cos^2 x in each case.
    Step 2 : Put tanxt dt
    at bt c


    ∫ ++
    to get the form 2 which
    is already discussed.
    INTEGRALS OF THE FORM
    (i) dx
    ∫axb xsin + cos
    (ii)
    dx
    ∫ab x+ sin
    (iii)
    dx
    ∫ab x+ cos (iv)
    dx
    ∫axb xcsin ++cos
    For all the cases (i), (ii), (iii) and (iv), universal
    substitutiontan , sin tan( / )
    tan ( / )
    x tx x
    2 x
    22
    122




  • &
    cos tan ( / )
    tan ( / )
    x x
    x
    = −




  • 12
    12
    2
    2 are used. This substitution convert
    the integrals in the form dt
    ∫at (^2) ++bt c
    .
    In (i), (ii) and (iii); if a = b, then they becomes
    11
    1
    1
    a 1
    dx
    xxa
    dx
    xa
    dx
    sin cos x
    ,
    sin
    ,
    ∫∫+++∫ cos
    FUNDAMENTAL THEOREM ON CALCULUS
    I. Let f be a continuous function on closed
    interval [α, β] and A(x) be the area of function.
    Then A′(x) = f(x) ∀ x ∈ [α, β]
    II. Let f be the continuous function on closed
    interval [α, β] and F be an anti-derivative of f.
    Then ∫fx dx Fx() =[]()αβ=F() ( )−F
    α
    β
    βα
    DEFINITE INTEGRAL AS THE LIMIT OF A SUM
    An alternative method of finding fx dx()
    α
    β
    ∫ is that
    the definite integral fx dx()
    α
    β
    ∫ is a limiting case of
    the summation of an infinite series provided f(x) is
    continuous on [α, β], i.e.,
    fxdx( ) lim [ ( )h hf f( h) ... f( (n ) )]h
    α
    β
    ∫ =+++++→ 0 αα α−^1
    where h
    n
    =βα−
    PROPERTIES OF DEFINITE INTEGRALS
    (i) ∫∫f x dx() = f t dt()
    α
    β
    α
    β
    (ii) ∫∫αfx dx() =− fx dx()
    β
    β
    α
    (iii) (a) ∫∫∫fxdx() =+fxdx() fxdx() , <<
    α
    β
    α
    γ
    γ
    β
    whereαγβ
    (b) fx dx fx dx fx dx fx dx
    c
    c c
    c
    n
    ∫∫() =+ ++() ∫ () ...∫()
    α
    β
    α
    1 β
    1
    2
    (iv) ∫∫f x dx() = f(−x dx)
    00
    αα
    α
    (v) ∫∫f x dx() =+f( −x dx)
    α
    β
    α
    β
    αβ
    (vi) fx dx
    fxdx f x fx
    fx fx
    ()
    () , ( ) ()
    ,()()


    − =
    − =−



    ⎩⎪
    −∫

    α
    α
    α
    2
    0
    0
    if
    if
    (vii) fxdx fxdx f x fx
    fxfx
    ()
    () , ( ) ()
    ,()()


    − =
    − =−



    ⎩⎪
    ∫ ∫
    0
    2
    0
    22
    02
    α α α
    α
    if
    if
    (viii) If f(t) is an odd function then gx ftdt
    a
    x
    ()=∫ ()
    is an even function.
    (ix) If f(t) is an even function then gxftdt
    x
    ()=∫ ()
    is an odd function.^0



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