A function composition problem

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Homework Help Overview

The problem involves the composition of functions, specifically determining the value of \( (g \circ f)(x) \) where \( f(x) = \sin^2 x + \sin^2(x + \pi/3) + \cos x \cos(x + \pi/3) \) and \( g(5/4) = 1 \). The challenge arises from the lack of a defined function \( g(x) \) beyond the given point.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the need to evaluate \( f(x) \) and its implications for \( g(x) \). There is confusion regarding the significance of \( g(5/4) \) and how it relates to the composition. Some suggest simplifying \( f(x) \) using trigonometric identities.

Discussion Status

Participants are actively engaging with the problem, attempting to simplify \( f(x) \) and questioning the role of the given \( g(5/4) \). There is recognition of the need for careful simplification, and some participants express gratitude for suggestions that guide their thought process.

Contextual Notes

There is an emphasis on the missing definition of \( g(x) \), which is central to resolving the problem. The discussion reflects uncertainty about how to proceed without additional information about \( g(x) \).

Raghav Gupta
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Homework Statement


If ## f(x) = sin^2x + sin^2(x+ π/3) + cosxcos(x+ π/3) ## and $$g(5/4)=1$$, then ##(gof)(x)## is equal to?
Options are
0
1
sinx
None of these

Homework Equations


I know gof(x) is g(f(x)) but here g(x) is not given.

The Attempt at a Solution


Basically I think we have to put f(x) value in g(x) but here g(x) is not given,
What's the use of g(5/4) ?
 
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Raghav Gupta said:

Homework Statement


If ## f(x) = sin^2x + sin^2(x+ π/3) + cosxcos(x+ π/3) ## and $$g(5/4)=1$$, then ##(gof)(x)## is equal to?
Options are
0
1
sinx
None of these

Homework Equations


I know gof(x) is g(f(x)) but here g(x) is not given.

The Attempt at a Solution


Basically I think we have to put f(x) value in g(x) but here g(x) is not given,
What's the use of g(5/4) ?
Use trig sum formulas to simplify ## f(x) = sin^2x + sin^2(x+ π/3) + cosxcos(x+ π/3) ##. If you're careful, you can get this simplfied a great deal.
 
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Mark44 said:
Use trig sum formulas to simplify ## f(x) = sin^2x + sin^2(x+ π/3) + cosxcos(x+ π/3) ##. If you're careful, you can get this simplfied a great deal.
By simplifying I got,
## 5/4 + \frac{√3}{2}sin2x ##.
 
Sorry, carefulness was required as you said.
Got on simplifying now 5/4, and then the answer is 1.
Thanks for the motivation of simplifying.
 
Raghav Gupta said:
Sorry, carefulness was required as you said.
Got on simplifying now 5/4, and then the answer is 1.
Thanks for the motivation of simplifying.
Yes, that's what I got as well.
 
Since the only g value you were given was "5/4", if this problem had an answer it had to be 5/4! Of course, you needed Mark44's suggestion to show that it had a solution.
 
Ya sometimes applying common sense is of great use but I was thinking something else.
 

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