# SOLVE FOR X with a sinx in it

• Oct 7th 2009, 09:13 AM
colmex
SOLVE FOR X with a sinx in it
"If f(x)= x² + 10*sin(x), show that there is a number c such that f(c)=1000"

so its asking to solve for x when f(x)=1000 right?
• Oct 7th 2009, 09:18 AM
6DOM
Quote:

Originally Posted by colmex
"If f(x)= x² + 10*sin(x), show that there is a number c such that f(c)=1000"

so its asking to solve for x when f(x)=1000 right?

Solving for x would be a proof
• Oct 7th 2009, 03:02 PM
awkward
Quote:

Originally Posted by colmex
"If f(x)= x² + 10*sin(x), show that there is a number c such that f(c)=1000"

so its asking to solve for x when f(x)=1000 right?

Not exactly.

The problem is asking you to show a solution exists, but it does not ask you to find it.

Sometimes it is easy to show the existence of a solution but hard to actually find the solution. If you can find a solution, great-- that certainly proves its existence.
• Oct 7th 2009, 06:25 PM
colmex
ohhhhhhhhhhhh okay
so how do i prove it? haha
• Oct 7th 2009, 07:27 PM
mr fantastic
Quote:

Originally Posted by colmex
ohhhhhhhhhhhh okay
so how do i prove it? haha

Use the Intermediate Value Theorem.