Answer:
4. b
5. a
Step-by-step explanation:
C is Heron's formula, area formula for triangle and it does not involve sine
On no. 5, the formula for law of cosine is
c2 = a2 + b2 − 2ab cos(C)
wherein 'C' reperesents an angle while the other three variables (a,b,c) are the length of two sides.
Therefore, Choice A is the answer
