1. Given any triangle ABC with sides BC=a, AC=b and AB=c, the following are true :
i) the larger the angle, the larger the side in front of it, and the other way around as well. (Sine Law) Let a=20 in, then the largest angle is angle A.
ii) Given the measures of the sides of a triangle. Then the cosines of any of the angles can be found by the following formula:

2.

3. m(A) = Arccos(-0.641)≈130°,
4. Remark: We calculate Arccos with a scientific calculator or computer software unless it is one of the well known values, ex Arccos(0.5)=60°, Arccos(-0.5)=120° etc
The answer to this question is b
The probability of getting the correct order in the spelling bee is 1 chance in 362,880.
This is a permutation problem. Our goals is to find the total number of ways that the 9 students can be ordered.
For the first spot there are 9 choices, then 8 choices, then 7 choices....
We need to evaluate:
9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 = 362,880
Another way to write this is: 9!