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Monday, November 16, 2015

Is there a real number x, that the expressions tanx+3 and cotx+3 are both integers?

Is there a real number x, that the expressions tanx+3 and cotx+3 are both integers?

My solution:

First, let's assume tanx+3=a and cotx+3=b where a,b are both integers.

From the second equality, we get:

cotx+3=b

cotx=b3

1tanx=b3

tanx=1b3

so we get

tanx=1b3=a3

(a3)(b3)=1

3=ab+2a+b

But recall that both a,b are both integers, this last equality contradicts to our previous assumption and so the answer is nope.

There isn't any real x that serves both the given two expressions to be integers.

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