Evaluate the following integral:
$\int \frac{1}{\sin ^{4} x+\sin ^{2} x \cos ^{2} x+\cos ^{4} x} d x$
Re-writing the given equation as
Multiplying $\sec ^{4} x$ in both numerator and denominator
$\int \frac{\sec ^{4} x}{\tan ^{4} x+\tan ^{2} x+1} d x$
$=\int \frac{\left(\tan ^{2} x+1\right) \sec ^{2} x}{\tan ^{4} x+\tan ^{2} x+1} d x$
Assume $\tan x=t$
$\sec ^{2} x d x=d t$
$=\int \frac{\left(\mathrm{t}^{2}+1\right) \mathrm{dt}}{\mathrm{t}^{4}+\mathrm{t}^{2}+1}$
$=\int \frac{1+\frac{1}{\mathrm{t}^{2}}}{\mathrm{t}^{2}+1+\frac{1}{\mathrm{t}^{2}}} \mathrm{dt}$
$=\int \frac{1+\frac{1}{\mathrm{t}^{2}}}{\left(\mathrm{t}-\frac{1}{\mathrm{t}}\right)^{2}+3} \mathrm{dt}$
Assume $\mathrm{z}=\mathrm{t}-\frac{1}{\mathrm{t}}$
$\Rightarrow \mathrm{dz}=1+\frac{1}{\mathrm{t}^{2}}$
$=\int \frac{\mathrm{dz}}{\mathrm{z}^{2}+3}$
Using identity $\int \frac{1}{x^{2}+1} d x=\arctan (x)$
$=\frac{1}{\sqrt{3}} \arctan \left(\frac{\mathrm{z}}{\sqrt{3}}\right)+\mathrm{c}$
$=\frac{1}{\sqrt{3}} \arctan \left(\frac{\mathrm{t}-\frac{1}{\mathrm{t}}}{\sqrt{3}}\right)+\mathrm{c}$
$=\frac{1}{\sqrt{3}} \arctan \left(\frac{\tan x-\frac{1}{\tan x}}{\sqrt{3}}\right)+c$
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All Study Material
- JEE Main
- Exam Pattern
- Previous Year Papers
- PYQ Chapterwise
- Physics
- Kinematics 1D
- Kinemetics 2D
- Friction
- Work, Power, Energy
- Centre of Mass and Collision
- Rotational Dynamics
- Gravitation
- Calorimetry
- Elasticity
- Thermal Expansion
- Heat Transfer
- Kinetic Theory of Gases
- Thermodynamics
- Simple Harmonic Motion
- Wave on String
- Sound waves
- Fluid Mechanics
- Electrostatics
- Current Electricity
- Capacitor
- Magnetism and Matter
- Electromagnetic Induction
- Atomic Structure
- Dual Nature of Matter
- Nuclear Physics
- Radioactivity
- Semiconductors
- Communication System
- Error in Measurement & instruments
- Alternating Current
- Electromagnetic Waves
- Wave Optics
- X-Rays
- All Subjects
- Physics
- Motion in a Plane
- Law of Motion
- Work, Energy and Power
- Systems of Particles and Rotational Motion
- Gravitation
- Mechanical Properties of Solids
- Mechanical Properties of Fluids
- Thermal Properties of matter
- Thermodynamics
- Kinetic Theory
- Oscillations
- Waves
- Electric Charge and Fields
- Electrostatic Potential and Capacitance
- Current Electricity
- Thermoelectric Effects of Electric Current
- Heating Effects of Electric Current
- Moving Charges and Magnetism
- Magnetism and Matter
- Electromagnetic Induction
- Alternating Current
- Electromagnetic Wave
- Ray Optics and Optical Instruments
- Wave Optics
- Dual Nature of Radiation and Matter
- Atoms
- Nuclei
- Semiconductor Electronics: Materials, Devices and Simple Circuits.
- Chemical Effects of Electric Current,