☰ Contents · Mathematics

The table of integrals and the simplest rules

Lessons 14 · 1 lessons · M. A. Mirzaahmedov, Sh. N. Ismailov, A. Q. Amanov (algebra and analysis), B. Q. Haydarov (geometry). Mathematics Grade 11, Parts 1 and 2, 1st edition. ZAMIN NASHR, Tashkent, 2018
14

Table of integrals and the simplest rules of integration

Textbook, Part 1: pp. 86–95
GoalCompute indefinite integrals with the table of integrals, the simplest rules, the formulas for a linear argument (kx + b) and a simple substitution.
New words
table of integrals · integrallar jadvaliintegral of a sum · yig‘indining integralisubstitution · o‘zgaruvchini almashtirishchecking by differentiation · tekshirish (differensiallash)
Explanation

Table: ∫ xᵖ dx = xᵖ⁺¹/(p + 1) + C (p ≠ −1); ∫ dx/x = ln|x| + C; ∫ eˣ dx = eˣ + C; ∫ aˣ dx = aˣ/ln a + C; ∫ sin x dx = −cos x + C; ∫ cos x dx = sin x + C; ∫ dx/cos²x = tan x + C; ∫ dx/sin²x = −cot x + C. Linear argument: if ∫ f(x) dx = F(x) + C then ∫ f(kx + b) dx = (1/k)F(kx + b) + C (k ≠ 0); for example ∫ cos(kx + b) dx = (1/k) sin(kx + b) + C. Rules: ∫ a·f dx = a ∫ f dx; ∫ (f ± g) dx = ∫ f dx ± ∫ g dx. The integral of a product is not the product of the integrals. For more complicated integrals substitute a new variable: for example u = x² + 5 gives du = 2x dx. If needed, simplify the integrand with trigonometric identities (cos²x = (1 + cos 2x)/2 and others). Always check the answer by differentiating.

Worked examples
∫ (4x³ − 6x + 5/x²) dx = x⁴ − 3x² − 5/x + C, because 5/x² = 5x⁻² and ∫ x⁻² dx = −1/x. Also ∫ (e³ˣ + cos(2x − 1)) dx = e³ˣ/3 + (1/2) sin(2x − 1) + C.
∫ 2x/(x² + 5) dx: u = x² + 5, du = 2x dx ⇒ ∫ du/u = ln(x² + 5) + C (x² + 5 > 0). ∫ cos²x dx: cos²x = (1 + cos 2x)/2 ⇒ x/2 + (sin 2x)/4 + C. Check: (x/2 + sin 2x/4)′ = 1/2 + cos 2x/2 = cos²x.
Class activity

“The integral is the mirror of the derivative”: pairs turn 6 rows of the derivative table into rows of the integral table. Then they make up 3 integrals for another pair, who check the answers by differentiating.

Practice
1
Compute ∫ (9x² + 2x − 3) dx.
2
Find ∫ sin 5x dx.
3
Compute ∫ (4x − 1)³ dx.
4
Why is ∫ x · x dx ≠ (∫ x dx) · (∫ x dx)? Check it.