Functions 2 Question 9

10. If gf(x)=|sinx| and fg(x)=(sinx)2, then

(a) f(x)=sin2x,g(x)=x

(1998, 2M)

(b) f(x)=sinx,g(x)=|x|

(c) f(x)=x2,g(x)=sinx

(d) f and g cannot be determined

Show Answer

Answer:

Correct Answer: 10. (a)

Solution:

  1. Let

f(x)=sin2x and g(x)=x

Now, fg(x)=f[g(x)]=f(x)=sin2x

and gf(x)=g[f(x)]=g(sin2x)=sin2x=|sinx|

Again, let f(x)=sinx,g(x)=|x|

fg(x)=f[g(x)]=f(|x|)=sin|x|(sinx)2

When

f(x)=x2,g(x)=sinx

fg(x)=f[g(x)]=f(sinx)=(sinx)2

and

(gf)(x)=g[f(x)]=g(x2)=sinx2

=sin|x||sinx|



जेईई के लिए मॉक टेस्ट

एनसीईआरटी अध्याय वीडियो समाधान

दोहरा फलक