Given that the formula is Cos θ = adj/hyp. We cannot apply the formula until we know what is the length of the hypotenuse.
To find hypotenuse, we will use the Pythagoras theorem:
a² + b² = c²
Substitute a = 6 and b = 8, we will be able to find c.
6² + 8² = c²
c² = 36 + 64
c² = 100
c = √100
c = 10
Now that we know that the hypotenuse is 10 units, we can find cos B:
Cos B = adj/hyp
Cos B = 8/10
Cos B = 4/5
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Answer: Cos B = 4/5
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