Answer:
The surface area is
![288\ cm^(2)](https://img.qammunity.org/2020/formulas/mathematics/high-school/fs9xscjnrjthtqjk1rtku76mko5mgstu3h.png)
Explanation:
we know that
The surface area of the square pyramid is equal to the area of the square base plus the area of its four triangular lateral faces
so
![SA=b^(2) +4[((1)/(2)) (b)(h)]](https://img.qammunity.org/2020/formulas/mathematics/high-school/owf8j4gaqkidi3onjzxyj6n4yk4t1wd9bl.png)
where
b is the length side of the square base
h is the height of each lateral triangular face
we know that
-----> by angle of 45 degrees
![sin(45\°)=(h)/(6√(2))](https://img.qammunity.org/2020/formulas/mathematics/high-school/um2vmfec3jzhks4bmxzg96dmpaerb7d7rh.png)
![h=6√(2)(sin(45\°)](https://img.qammunity.org/2020/formulas/mathematics/high-school/bdrs56u50dhzv3rcuehkj1s6jdfjbdwffi.png)
![h=6\ cm](https://img.qammunity.org/2020/formulas/mathematics/college/a3qvq5m7nxmkdslmfc1vl7mwdij6j7soi4.png)
Find the value of b
![b=2h=2(6)=12\ cm](https://img.qammunity.org/2020/formulas/mathematics/high-school/wffp93gwm2efd50a8exe4o5pdu0me6volv.png)
Find the surface area
![SA=12^(2) +4[((1)/(2)) (12)(6)]=288\ cm^(2)](https://img.qammunity.org/2020/formulas/mathematics/high-school/q25symdxrz0uekdgw2h7a8qb88rzq2ffld.png)