Basic Math Formulas for 11th and 12th continue..............
● Surds:
(i) The surd conjugate of √a + √b (or a + √b) is √a - √b (or a - √b) and conversely.
(ii) If a is rational, √b is a surd and a + √b (or, a - √b) = 0 then a = 0 and b = 0.
(iii) If a and x are rational, √b and √y are surds and a + √b = x + √y then a = x and b = y.
● Complex Numbers:
(i) The symbol z = (x, y) = x + iy where x, y are real and i = √-1, is called a complex (or, imaginary) quantity;x is called the real part and y, the imaginary part of the complex number z = x + iy.
(ii) If z = x + iy then z = x - iy and conversely; here, z is the complex conjugate of z.
(iii) If z = x+ iy then
(a) mod. z (or, | z | or, | x + iy | ) = + √(x2 + y2) and
(b) amp. z (or, arg. z) = Ф = tan-1 y/x (-π < Ф ≤ π).
(iv) The modulus - amplitude form of a complex quantity z is
z = r (cosф + i sinф); here, r = | z | and ф = arg. z (-π < Ф <= π).
(v) | z | = | -z | = z ∙ z = √ (x2 + y2).
(vi) If x + iy= 0 then x = 0 and y = 0(x,y are real).
(vii) If x + iy = p + iq then x = p and y = q(x, y, p and q all are real).
(viii) i = √-1, i2 = -1, i3 = -i, and i4 = 1.
(ix) | z1 + z2| ≤ | z1 | + | z2 |.
(x) | z1 z2 | = | z1 | ∙ | z2 |.
(xi) | z1/z2| = | z1 |/| z2 |.
(xii) (a) arg. (z1 z2) = arg. z1 + arg. z2 + m
(b) arg. (z1/z2) = arg. z1 - arg. z2 + m where m = 0 or, 2π or, (- 2π).
(xiii) If ω be the imaginary cube root of unity then ω = ½ (- 1 + √3i) or, ω = ½ (-1 - √3i)
(xiv) ω3 = 1 and 1 + ω + ω2 = 0
● Variation:
(i) If x varies directly as y, we write x ∝ y or, x = ky where k is a constant of variation.
(ii) If x varies inversely as y, we write x ∝ 1/y or, x = m ∙ (1/y) where m is a constant of variation.
(iii) If x ∝ y when z is constant and x ∝ z when y is constant then x ∝ yz when both y and z vary.
● Theory of Quadratic Equation :
ax2 + bx + c = 0 ... (1)
(i) Roots of the equation (1) are x = {-b ± √(b2 – 4ac)}/2a.
(ii) If α and β be the roots of the equation (1) then,
sum of its roots = α + β = - b/a = - (coefficient of x)/(coefficient of x2 );
and product of its roots = αβ = c/a = (Constant term /(Coefficient of x2).
(iii) The quadratic equation whose roots are α and β is
x2 - (α + β)x + αβ = 0
i.e. , x2 - (sum of the roots) x + product of the roots = 0.
(iv) The expression (b2 - 4ac) is called the discriminant of equation (1).
(v) If a, b, c are real and rational then the roots of equation (1) are
(a) real and distinct when b2 - 4ac > 0;
(b) real and equal when b2 - 4ac = 0;
(c) imaginary when b2 - 4ac < 0;
(d) rational when b2- 4ac is a perfect square and
(e) irrational when b2 - 4ac is not a perfect square.
(vi) If α + iβ be one root of equation (1) then its other root will be
conjugate complex quantity α - iβ and conversely (a, b, c are real).
(vii) If α + √β be one root of equation (1) then its other root will be
conjugate irrational quantity α - √β (a, b, c are rational).
● Permutation:
(i) ⌊n (or, n!) = n (n – 1) (n – 2) ∙∙∙∙∙∙∙∙∙ 3∙2∙1.
(ii) 0! = 1.
(iii) Number of permutations of n different things taken r ( ≤ n) at a time nPr = n!/(n - 1)! = n (n – 1)(n - 2) ∙∙∙∙∙∙∙∙ (n - r + 1).
(iv) Number of permutations of n different things taken all at a time = nPn = n!.
(v) Number of permutations of n things taken all at a time in which p
things are alike of a first kind, q things are alike of a second kind, r
things are alike of a third kind and the rest are all different, is n!/(p!q!r!)
(vi) Number of permutations of n different things taken r at a time when each thing may be repeated upto r times in any permutation, is nr .
● Combination:
(i) Number of combinations of n different things taken r at a time = nCr = n!/(r!(n – r)!).
(ii) nPr = r!∙ nCr.
(iii) nC0 = nCn = 1.
(iv) nCr = nCn - r.
(v) nCr + nCn - 1 = n + 1Cr
(vi) If p ≠ q and nCp = nCp then p + q = n.
(vii) nCr/nCr - 1= (n - r + 1)/r.
(viii) The total number of combinations of n different things taken any number at a time = nC1 + nC2 + nC3 + …………. + nCn = 2n – 1.
(ix) The total number of combinations of (p + q + r + . . . .) things of
which p things are alike of a first kind, q things are alike of a
second kind r things are alike of a third kind and so on, taken any
number at a time is [(p + 1) (q + 1) (r + 1) . . . . ] - 1.
● Binomial Theorem:
(i) Statement of Binomial Theorem : If n is a positive integer then
(a + x)n = an + nC1 an - 1 x + nC2 an - 2 x2 + …………….. + nCr an - r xr + ………….. + xn …….. (1)
(ii) If n is not a positive integer then
(1 + x)n = 1 + nx + [n(n - 1)/2!] x2 + [n(n - 1)(n - 2)/3!] x3 + ………… + [{n(n-1)(n-2)………..(n-r+1)}/r!] xr+ ……………. ∞ (-1 < x < 1) ………….(2)
(iii) The general term of the expansion (1) is (r+ 1)th term
= tr + 1 = nCr an - r xr
(iv) The general term of the expansion (2) is (r + 1) th term
= tr + 1 = [{n(n - 1)(n - 2)....(n - r + l)}/r!] ∙ xr.
(v) There is one middle term is the expansion ( 1 ) when n is even and
it is (n/2 + 1)th term ; the expansion ( I ) will have two middle terms
when n is odd and they are the {(n - 1)/2 + 1} th and {(n - 1)/2 + 1} th
terms.
(vi) (1 - x)-1 = 1 + x + x2 + x3 + ………………….∞.
(vii) (1 + x)-1 = I - x + x2 - x3 + ……………∞.
(viii) (1 - x)-2 = 1 + 2x + 3x2 + 4x3 + . . . . ∞ .
(ix) (1 + x)-2 = 1 - 2x + 3x2 - 4x3 + . . . . ∞ .
● Logarithm:
(i) If ax = M then loga M = x and conversely.
(ii) loga 1 = 0.
(iii) loga a = 1.
(iv) a logam = M.
(v) loga MN = loga M + loga N.
(vi) loga (M/N) = loga M - loga N.
(vii) loga Mn = n loga M.
(viii) loga M = logb M x loga b.
(ix) logb a x 1oga b = 1.
(x) logb a = 1/logb a.
(xi) logb M = logb M/loga b.
● Exponential Series:
(i) For all x, ex = 1 + x/1! + x2/2! + x3/3! + …………… + xr/r! + ………….. ∞.
(ii) e = 1 + 1/1! + 1/2! + 1/3! + ………………….. ∞.
(iii) 2 < e < 3; e = 2.718282 (correct to six decimal places).
(iv) ax = 1 + (loge a) x + [(loge a)2/2!] ∙ x2 + [(loge a)3/3!] ∙ x3 + …………….. ∞.
● Logarithmic Series:
(i) loge (1 + x) = x - x2/2 + x3/3 - ……………… ∞ (-1 < x ≤ 1).
(ii) loge (1 - x) = - x - x2/ 2 - x3/3 - ………….. ∞ (- 1 ≤ x < 1).
(iii) ½ loge [(1 + x)/(1 - x)] = x + x3/3 + x5/5 + ……………… ∞ (-1 < x < 1).
(iv) loge 2 = 1 - 1/2 + 1/3 - 1/4 + ………………… ∞.
(v) log10 m = µ loge m where µ = 1/loge 10 = 0.4342945 and m is a positive num
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