100 POINTS 5 STARS AND A THANKS

When keisha installed a fence along the 200 foot perimeter of her rectangular back yard, she left an opening for a gate. in the diagram below, she used x to represent the length in feet of the gate? what is the value? a. 10 b. 20 c. 25 d. 30

What’s the answer ? use the picture to see the problem

Prove sin2a + cos2a - 1 / sin2a + cos2a + 1 = 1 - tana / 1 + cota