Answer:
Step-by-step explanation:
The answer is 50 I got it right
Perimeter Formula:

Area Formula:

Set perimeter Formula equal to b:

Plug formula for be we just made above into the area Formula:

Solve for L (you'll have to use quadratic formula) then plug that back into the area Equation and solve for b.
Here's a link to where the problem has been explained before (they go into more detail than me).
https://brainly.ph/question/468631
lmk if you need any more help
We have:

Then we use trigonometric identities to change the negative sign of the trigonometric functions, so:

We clear f(x):

we simply what we can:

Thus, the correct answer is;