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If int(a)^(b)|sin|dx=8& int(0)^(a+b)|cos...

If `int_(a)^(b)|sin|dx=8`& `int_(0)^(a+b)|cosx|dx=9` ten

A

`a+b=9pi`

B

`b-a=4pi`

C

`int_(a)^(b)x sin x dx = 2 sqrt (2)pi`

D

`int_(a)^(b) x si x dx =-2sqrt(pi)`

Text Solution

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The correct Answer is:
To solve the problem, we need to analyze the given integrals and find the relationships between the variables \( a \) and \( b \). ### Step 1: Analyze the first integral We are given: \[ \int_a^b |\sin x| \, dx = 8 \] The integral of \( |\sin x| \) over one complete period \( [0, \pi] \) is: \[ \int_0^\pi |\sin x| \, dx = 2 \] This means that over the interval \( [0, \pi] \), the area under \( |\sin x| \) is 2. To find how many complete periods fit into the interval \( [a, b] \), we can express the integral as: \[ \int_a^b |\sin x| \, dx = n \cdot 2 \] where \( n \) is the number of complete periods. Setting this equal to 8, we have: \[ n \cdot 2 = 8 \implies n = 4 \] Thus, the interval \( [a, b] \) spans 4 complete periods of \( |\sin x| \), which corresponds to: \[ b - a = 4\pi \] This gives us our first equation: \[ b - a = 4\pi \quad \text{(Equation 1)} \] ### Step 2: Analyze the second integral Next, we have: \[ \int_0^{a+b} |\cos x| \, dx = 9 \] The integral of \( |\cos x| \) over one complete period \( [0, \pi] \) is also: \[ \int_0^\pi |\cos x| \, dx = 2 \] Thus, we can express the integral as: \[ \int_0^{a+b} |\cos x| \, dx = m \cdot 2 \] where \( m \) is the number of complete periods. Setting this equal to 9, we have: \[ m \cdot 2 = 9 \implies m = \frac{9}{2} = 4.5 \] This means that the interval \( [0, a+b] \) spans 4.5 periods of \( |\cos x| \), which corresponds to: \[ a + b = 4.5\pi \] This gives us our second equation: \[ a + b = 4.5\pi \quad \text{(Equation 2)} \] ### Step 3: Solve the system of equations Now, we have two equations: 1. \( b - a = 4\pi \) 2. \( a + b = 4.5\pi \) We can solve this system of equations. From Equation 1, we can express \( b \) in terms of \( a \): \[ b = a + 4\pi \] Substituting this into Equation 2: \[ a + (a + 4\pi) = 4.5\pi \] This simplifies to: \[ 2a + 4\pi = 4.5\pi \] Subtracting \( 4\pi \) from both sides: \[ 2a = 0.5\pi \implies a = \frac{0.5\pi}{2} = \frac{\pi}{4} \] Now substituting \( a \) back into the expression for \( b \): \[ b = \frac{\pi}{4} + 4\pi = \frac{\pi}{4} + \frac{16\pi}{4} = \frac{17\pi}{4} \] ### Final Values Thus, we find: \[ a = \frac{\pi}{4}, \quad b = \frac{17\pi}{4} \]

To solve the problem, we need to analyze the given integrals and find the relationships between the variables \( a \) and \( b \). ### Step 1: Analyze the first integral We are given: \[ \int_a^b |\sin x| \, dx = 8 \] The integral of \( |\sin x| \) over one complete period \( [0, \pi] \) is: ...
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