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Q. (iii) If f (x) = 1 - sin   x π - 2 x 2 ,   w h e n   x π 2   K ,   w h e n   x = π 2
Find the value of K for which f (x) is continuous at x = π 2 .
Ans : 1 2

LHL = limxπ2- fx=limxπ2- 1 - sin xπ - 2x2Put x = π2 - has, x  π2-, h0LHL = limh01 - sinπ2 - hπ - 2π2 - h= limh01 - cos h4h2=14 limh02 sin2h/2h2=12 limh0sinh/2h/2×12×limh0sinh/2h/2×12=12×1×12×1×12=18RHL = limxπ2+ fx=limxπ2+ 1 - sin xπ - 2x2Put x = π2 + has, x  π2+, h0RHL = limh01 - sinπ2 + hπ - 2π2 + h= limh01 - cos h4h2=14 limh02 sin2h/2h2=12 limh0sinh/2h/2×12×limh0sinh/2h/2×12=12×1×12×1×12=18Now, fπ2 = kSince, f is continuous at x = π2, thenLHL = RHL = fπ2k = 18

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