Answer:
steps below
Step-by-step explanation:
Are you going to solve the value of A or just a proof the equation
cos 2A = cos² A - sin² A
2cos²A-cos2A-1 = 2cos²A - (cos² A - sin² A) - 1 = cos² A + sin² A - 1
2cos²A-cos2A-1 = 1 - 1 = 0
A: 90° or 270° or 450° .....
You need to provide a picture or something
The figure is a parallelogram, and in a parallelogram, the lower side and the upper side have the same length. Also, the left side and the right side have the same length. This is shown in the following image:
The red sides are equal, and the blue sides are equal.
Thus, since the blue sides are equal, we can use the following equation to find x:

And since, once we know x, we can know the length of JK, this is the equation that we can use to find JK.
Answer:
7x=3x+14
the measure is 140, I basically summed all of the angles of a polygon of “n”, which is 7, then I did 7-2 times 180 (900) so I can finally add up all of your measurements