Answer:
D. m < A = 50 degrees, b = 20, c = 18
Explanation:
Solution Given:
The formula of Cosine is:
c² = a²+ b² − 2ab cos(C).
a²=b²+c²-2bc cos(A)
b²=a²+c²+2ac cos(B)
If you draw a triangle ABC, then side AB is equal to c, side BC is equal to a, and side AC is equal to b.
a is opposite angle A.
b is opposite angle B.
c is opposite angle C.
If a is opposite angle A, then angle A has to be included between sides b and c.
If b is opposite angle B, then angle B has to be included between sides a and c
If c is opposite angle C, then angle C has to be included between sides a and b.
Therefore, Answer is:
D. m < A = 50 degrees, b = 20, c = 18
Side a is opposite angle which means that angle A is included between sides b and c.