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#1 2007-10-25 07:11:40

xXxEmZyxXx
Member
Registered: 2007-10-15
Posts: 12

functions

F(x)=5sin(2x)-2cosx

is this funtion R->R
injective, surjective, or both anyone know and can show me how to determine for future references

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#2 2007-10-25 07:31:18

JaneFairfax
Member
Registered: 2007-02-23
Posts: 6,868

Re: functions

It is a function from

to
.

It is not injective because e.g.

It is not surjective because the maximum value of 5sin2x is 5 and the meximum value of −2cosx is 2, so their sum isn’t going to exceed 7 – hence there is no x such that F(x) = 8.

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#3 2007-10-30 06:21:46

xXxEmZyxXx
Member
Registered: 2007-10-15
Posts: 12

Re: functions

thanks but what properties of sine/cosine did you use to get the values of x???

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