# When does sin(x)/cos(x) equal 1

• July 15th 2012, 10:53 PM
KStudent
When does sin(x)/cos(x) equal 1
I have an equation where solutions to cos(x)=sin(x) are needed. I have been told that sin(x)/cos(x) is equal to tan(x) but also that sin(x)/cos(x)=1. For which value will sin(x)/cos(x) result in 1?
• July 15th 2012, 11:00 PM
richard1234
Re: When does sin(x)/cos(x) equal 1
Whenever tan x = 1. For which x is tan x = 1?
• July 15th 2012, 11:09 PM
KStudent
Re: When does sin(x)/cos(x) equal 1
tan^-1(1)?
• July 16th 2012, 04:21 AM
hemvanezi
Re: When does sin(x)/cos(x) equal 1
$sin^2x+cos^2x=1$
if sinx= cosx
$2 sin^2x=1$
$sinx= 1/SQRT2$
x=45 Deg
• July 16th 2012, 04:32 AM
Prove It
Re: When does sin(x)/cos(x) equal 1
I believe you'll find that adding all integer multiples of 180 degrees will also work.
• July 16th 2012, 11:14 AM
richard1234
Re: When does sin(x)/cos(x) equal 1
Another way to do it: On the unit circle, cos x corresponds to the x-coordinate and sin x corresponds to the y-coordinate. Therefore, $\sin x = \cos x$ if and only if the point on the unit circle is such that the x-coordinate equals the y-coordinate, or the point lies on the line y=x. Where does the unit circle intersect the line y=x?
• July 16th 2012, 11:36 AM
HallsofIvy
Re: When does sin(x)/cos(x) equal 1
Of course, $\frac{sin(x)}{cos(x)}= 1$ is the same as $sin(x)= cos(x)$. Since, in basic terms, "sine" and "cosine" refer to opposite angles in a right triangle, if they are equal those angles must be the same- and since those those angles must add to 90 degrees, it should be easy to see what the angle must be. In more advanced terms, where the angles are not in a right triangle, we can use the "circle" formulation and see that adding 180 degrees will also be an angle.
• July 17th 2012, 10:02 AM
Wilmer
Re: When does sin(x)/cos(x) equal 1
Quote:

Originally Posted by Prove It
I believe you'll find that adding all integer multiples of 180 degrees will also work.

D'you mean SIN(x)/COS(90-x) where 90 > x > 0 ?