Refer to the attached file.
Just replace cos2x with cos²x-sin²x
and work out.
I hope it helps u
I believe it's x= 20, hopes it help!
Use the formula....central angle/360= arc length/2* pie* R
150/360=x/2*3.14*7.5
150/360=x/47.1
360x=7065
x=7065/360
x=19.625 in
About half of the Pizza is left
Explanation
By subtracting what Marcy ate, i.e 2/9 of 2/3, we get 14/27 to be the remaining pizza. This is about half