The expression that is not a variation of the Pythagorean identity is the third option.
<h3>
What is the Pythagorean identity?</h3>
The Pythagorean identity can be written as:

For example, if we subtract cos^2(x) on both sides we get the second option:

Which is a variation.
Now, let's divide both sides by cos^2(x).

Notice that the third expression in the options looks like this one, but the one on the right side is positive. The above expression is in did a variation of the Pythagorean identity, then the one written in the options (with the 1 instead of the -1) is incorrect, meaning that it is not a variation of the Pythagorean identity.
Concluding, the correct option is the third one.
If you want to learn more about the Pythagorean identity, you can read:
brainly.com/question/24287773
Answer:
let
hypotenuse[h]=60ft
base[b]=36ft
perpendicular [p]=48ft
by using Pythagoras law
p²+b²=h²
48²+36²=60²
2896≠3600
since p²+b²≠ h²[<u>so</u><u> </u><u>the</u><u> </u><u>stage</u><u> </u><u>is</u><u> </u><u>not</u><u> </u><u>in</u><u> </u><u>a</u><u> </u><u>right</u><u> </u><u>angled</u><u> </u><u>tria</u><u>ngle</u><u>]</u><u>but</u><u> </u><u>it</u><u> </u><u>is</u><u> </u><u>scalene</u><u> </u><u>triangle</u>
1he answer is 42/98=3/7 and 16/38=8/19