Hope this helps
1. X= 4
2. X=7
3. 8.7x10^10
We will determine the surface area as follows:
![A=6(5cm\ast5cm)\Rightarrow A=150cm^2](https://tex.z-dn.net/?f=A%3D6%285cm%5Cast5cm%29%5CRightarrow%20A%3D150cm%5E2)
So, the total surface area is 150 cm^2.
First, we expand the equation:
![cos^{2}A+2cosAcosB+ cos^{2}B+sin^{2}A+2sinAsinB+sin^{2}B](https://tex.z-dn.net/?f=%20cos%5E%7B2%7DA%2B2cosAcosB%2B%20cos%5E%7B2%7DB%2Bsin%5E%7B2%7DA%2B2sinAsinB%2Bsin%5E%7B2%7DB)
Then, we combine certain terms in order to simplify them using trigonometry identities.
![cos^{2}A+sin^{2}A+cos^{2}B+sin^{2}B+2cosAcosB+2sinAsinB](https://tex.z-dn.net/?f=cos%5E%7B2%7DA%2Bsin%5E%7B2%7DA%2Bcos%5E%7B2%7DB%2Bsin%5E%7B2%7DB%2B2cosAcosB%2B2sinAsinB)
Note these identities:
Pythagoran relation:
![cos^{2}A+sin^{2}A = cos^{2}B+sin^{2}B=1](https://tex.z-dn.net/?f=cos%5E%7B2%7DA%2Bsin%5E%7B2%7DA%20%3D%20cos%5E%7B2%7DB%2Bsin%5E%7B2%7DB%3D1)
Sum and Difference Formula/Identities:
![cos(A-B) = cosAcosB+sinAsinB](https://tex.z-dn.net/?f=cos%28A-B%29%20%3D%20cosAcosB%2BsinAsinB)
Thus, if we apply these identities, the simplified equation would be:
![2(cos(A-B))+2](https://tex.z-dn.net/?f=2%28cos%28A-B%29%29%2B2)
Simplying further, the answer would be
I think 15 I am not 100 percent on that