Question

4) In A ABC, m B = 25°, b = 12 and c = 21. Find all possible m2 C to the
nearest degree.

Answer 1

47.7° or 132.3°

Explanation:

In A ABC, m B = 25°, b = 12 and c = 21. Find all possible mC to the

nearest degree.

We solve the above question using Laws of sines.

The formula is given as

b/sin B = c/sin C

b = 12

B = 25°

c = 21

C = ?

Hence:

12/sin 25 = 21/sin C

Cross Mulitiply

= 12 × sin C = sin 25 × 21

sin C = sin 25 × 21/12

C = arc sin (sin 25 × 21/12)

C = 47.7°

The second possible value of C =

180° - 47.7°

= 132.3°

Therefore, all the possible values of mC = 47.7° or 132.3°