Trigonometry » How do you see what side is the opposite, adjacent or hypotenuse?  


Working with tangent, sine and cosine is called trigonometry. Trigono is Greek for triangle, -metry means measuring.
In Dutch it is called 'goniometrie', where gonia is Greek for 'angle'.
With trigonometry, you always work in right-angled triangles.
In these triangles you have three sides, of which two intersect at a right angle.
These sides are called shorter sides.

Opposite side

The shorter side that is opposite of the angle you look from is called the opposite (shorter) side.
This side is not an arm of the angle you are looking from.

Adjacent side

The shorter side that is intersecting with the angle you look from is called the adjacent (shorter) side. This side is one of the arms of the angles you look from. This side HAS to be a shorter side.


The longest side in the triangle is called the hypotenuse.
This side is always opposite of the right angle.

Seen from angle signA: Information above in an example
Seen from angle signB: Information above in an example