To find the angle use arc tan (-5/-7) which simplifies tips arctan(5/7). arc tan is tan to the power -1, which is also called inverse tan. The heading of the angle, if you drew this out on a graph your angle would be in the third quadrant and therefore the heading is south of west.
The volume of the pyramid is 
Explanation:
The height of the square pyramid is 18 cm
The base of the square pyramid is 11 cm
The volume of the square pyramid can be determined using the formula,

Substituting
and
in the formula, we have,

Simplifying, we have,

Multiplying, we get,

Dividing, we get,

Thus, the volume of the pyramid is 
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