Answer:
20 degree
Step-by-step explanation:
x + x + 70 = 110 degree (sum of two opposite interior angle equal to the exterior angle formed)
2x = 110 - 70
x = 40/2
x = 20 degree
ANSWER
139°
EXPLANATION
One of the interior angle properties of a parallelogram is that adjacent interior angles are supplementary.
This means that, the adjacent interior angles add up to 180°.
If

Then

OR



Answer:
Part 1)
Bob's mistake was to have used the cosine instead of the sine
The measure of the missing angle is 
Part 2) The surface area of the pyramid is 
Step-by-step explanation:
Part 1)
Let
x----> the missing angle
we know that
In the right triangle o the figure
The sine of angle x is equal to divide the opposite side angle x to the hypotenuse of the right triangle


Bob's mistake was to have used the cosine instead of the sine
Part 2) 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 lateral triangular faces
so
![SA=b^{2}+4[\frac{1}{2}(b)(h)]](https://tex.z-dn.net/?f=SA%3Db%5E%7B2%7D%2B4%5B%5Cfrac%7B1%7D%7B2%7D%28b%29%28h%29%5D)
where
b is the length side of the square
h is the height of the triangular lateral face
In this problem
-------> by an 45° angle
so



Find the value of b

Find the surface area
![SA=12^{2}+4[\frac{1}{2}(12)(6)]=288\ cm^{2}](https://tex.z-dn.net/?f=SA%3D12%5E%7B2%7D%2B4%5B%5Cfrac%7B1%7D%7B2%7D%2812%29%286%29%5D%3D288%5C%20cm%5E%7B2%7D)
Step-by-step explanation:
it's an equilateral triangle so all sides are equal
using Pythagorean theorem
2(√6) raised to the power of 2 = √6 raised to the power of 2 + x raised to the power of 2
2(√6) raised to the power of 2 is 12
√6 raised to the power of 2 is 6
therefore 12=6 + x
x = 12-6
x=6