Find the numerical value of the log expression. log
a
3
c
2

b
7

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For this case we can use the law of cosine to determine the length of side b.
 We have then:
 b ^ 2 = a ^ 2 + c ^ 2 - 2 * a * c * cos (B)
 Substituting values we have:
 b ^ 2 = 4 ^ 2 + 5 ^ 2 - 2 * 4 * 5 * cos (60)
 Clearing b:
 b = root (4 ^ 2 + 5 ^ 2 - 2 * 4 * 5 * cos (60))
 
 an expression that is equivalent to the length of side b is:
 b = root (4 ^ 2 + 5 ^ 2 - 2 * 4 * 5 * cos (60))