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Q13:
By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19.
13. $\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \sin^7 x dx$
Solution :
Step 1: Identification of the Integrand Property
To evaluate the definite integral $I = \int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \sin^7 x \, dx$, we must first examine the parity of the function $f(x) = \sin^7 x$.
A function $f(x)$ is defined as even if $f(-x) = f(x)$ and odd if $f(-x) = -f(x)$.
Evaluating the function at $-x$:
$f(-x) = \sin^7(-x)$[By the trigonometric identity $\sin(-\theta) = -\sin(\theta)$]:
$f(-x) = (-\sin x)^7 = -(\sin^7 x)$ $f(-x) = -f(x)$Since $f(-x) = -f(x)$, the function $f(x) = \sin^7 x$ is an odd function.
Step 2: Application of Definite Integral Property
We utilize the standard property of definite integrals regarding symmetric intervals:
$\int_{-a}^{a} f(x) \, dx = \begin{cases} 2\int_{0}^{a} f(x) \, dx & \text{if } f(x) \text{ is even} \\ 0 & \text{if } f(x) \text{ is odd} \end{cases}$
[Per the property of definite integrals over symmetric intervals].
Step 3: Execution and Evaluation
Given the interval $[-\frac{\pi}{2}, \frac{\pi}{2}]$, where $a = \frac{\pi}{2}$, and having established that $\sin^7 x$ is an odd function:
$I = \int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \sin^7 x \, dx = 0$Visual Representation of the Odd Function
The graph shows the symmetry of $\sin^7 x$ across the origin. The area accumulated from $[-\frac{\pi}{2}, 0]$ is equal in magnitude but opposite in sign to the area accumulated from $[0, \frac{\pi}{2}]$, leading to a total sum of zero.
Final Solution: 0
More Questions from Class 12 Mathematics Integrals EXERCISE 7.10
- Q1: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 1. $\int_{0}^{\frac{\pi}{2}} \cos^2 x dx$
- Q2: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 2. $\int_{0}^{\frac{\pi}{2}} \frac{\sqrt{\sin x}}{\sqrt{\sin x} + \sqrt{\cos x}} dx$
- Q3: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 3. $\int_{0}^{\frac{\pi}{2}} \frac{\sin^{\frac{3}{2}} x dx}{\sin^{\frac{3}{2}} x + \cos^{\frac{3}{2}} x}$
- Q4: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 4. $\int_{0}^{\frac{\pi}{2}} \frac{\cos^5 x dx}{\sin^5 x + \cos^5 x}$
- Q5: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 5. $\int_{-5}^{5} |x+2| dx$
- Q6: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 6. $\int_{2}^{8} |x-5| dx$
- Q7: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 7. $\int_{0}^{1} x(1-x)^n dx$
- Q8: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 8. $\int_{0}^{\frac{\pi}{4}} \log(1+\tan x) dx$
- Q9: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 9. $\int_{0}^{2} x \sqrt{2-x} dx$
- Q10: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 10. $\int_{0}^{\frac{\pi}{2}} (2\log \sin x - \log \sin 2x) dx$
- Q11: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 11. $\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \sin^2 x dx$
- Q12: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 12. $\int_{0}^{\pi} \frac{x dx}{1+\sin x}$
- Q14: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 14. $\int_{0}^{2\pi} \cos^5 x dx$
- Q15: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 15. $\int_{0}^{\frac{\pi}{2}} \frac{\sin x - \cos x}{1+\sin x \cos x} dx$
- Q16: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 16. $\int_{0}^{\pi} \log(1+\cos x) dx$
- Q17: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 17. $\int_{0}^{a} \frac{\sqrt{x}}{\sqrt{x} + \sqrt{a-x}} dx$
- Q18: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 18. $\int_{0}^{4} |x-1| dx$
- Q19: By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19. 19. Show that $\int_{0}^{a} f(x) g(x) dx = 2 \int_{0}^{a} f(x) dx$, if $f$ and $g$ are defined as $f(x) = f(a-x)$ and $g(x) + g(a-x) = 4$
- Q20: Choose the correct answer in Exercises 20 and 21. 20. The value of $\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} (x^3 + x \cos x + \tan^5 x + 1) dx$ is
- Q21: Choose the correct answer in Exercises 20 and 21. 21. The value of $\int_{0}^{\frac{\pi}{2}} \log (\frac{4+3\sin x}{4+3\cos x}) dx$ is
CBSE Solutions for Class 12 Mathematics Integrals
- Integrals Class 12 EXERCISE 7.1
- Integrals Class 12 EXERCISE 7.2
- Integrals Class 12 EXERCISE 7.3
- Integrals Class 12 EXERCISE 7.4
- Integrals Class 12 EXERCISE 7.5
- Integrals Class 12 EXERCISE 7.6
- Integrals Class 12 EXERCISE 7.7
- Integrals Class 12 EXERCISE 7.8
- Integrals Class 12 EXERCISE 7.9
- Integrals Class 12 Miscellaneous Exercise on Chapter 7
Chapters in CBSE - Class 12 Mathematics
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