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ज्ञात करे[ Evalute]` int _(0)^(3//2) | x cos pi x | dx `

Answer» ` x cos pi x = 0 rArr {{:(x =0 ),(cos pix = 0 " या " pi x = (2n+1)pi/2 " , " n in Z ):}`
` rArr {{:( x=0 ),(x=1/2","0 " तथा " 3/2 " के बीच ") :}`
अब , ` int _(0)^(3//2) | x cos pi x | dx = int _(0)^(1//2) | x cos pix| dx + int _(1//2)^(3//2) | x cos pix | dx `
` = int _(0)^(1//2) x cos pi x dx - int _(1//2)^(3//2) x cos pix //dx`
` = [ (x sin pi x)/pi + (cos pix)/pi ]_(0)^(1//2) - [ (xsin pix)/pi+ (cos pix)/(pi^(2))]_(1//2)^(3//2)`
` = (1/(2pi)-1/(pi^(2)))-(-3/(2pi)-1/(2pi))= 1/(2pi) - 1/(pi^(2)) + 2/pi = 5/(2pi) - 1/(pi^(2))`


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