Answer:
63.6mm
Step-by-step explanation:
According to cosine rule;
AB² = BC²+AC²-2(BC)(AC)cos m<C
Substitute the given values
AB² = 70²+40²-2(70)(40)cos 64
AB² = 4900+1600-5600cos64
AB² = 6500-5600(0.4384)
AB² = 6500-2,454.87
AB² = 4,045.12
AB = √4,045.12
AB = 63.6mm
Hence the length of AB is 63.6mm
