Indefinite Integration 1 Question 46

47. Let f:R(0,1) be a continuous function. Then, which of the following function(s) has (have) the value zero at some point in the interval (0,1) ?

(2017 Adv.)

(a) ex0xf(t)sintdt

(b) f(x)+0π2f(t)sintdt

(c) x0f(t)costdt

(d) x9f(x)

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Solution:

  1. ex(1,e) in (0,1) and 0xf(t)sintdt(0,1) in (0,1)

ex0xf(t)sintdt cannot be zero.

So, option (a) is incorrect. (b) f(x)+0π2f(t)sintdt always positive

Option (b) is incorrect.

(c) Let h(x)=x02f(t)costdt,

h(0)=0π2f(t)costdt<0h(1)=10π21f(t)costdt>0

Option (c) is correct.

(d) Let g(x)=x9f(x)

g(0)=f(0)<0

g(1)=1f(1)>0

Option (d) is correct.



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