The measure of angle x will be 88 degrees. Then the correct option is C.
The complete question is attached below.
What is law of cosine?
Let there is a triangle ABC such that |AB| = a units, |AC| = b units, and |BC| = c units and the internal angle A is of θ degrees, then we have:
2ab cos θ = a² + b² – c²
The triangle is shown below.
Then the value of the variable x will be
2 · 7 · 10 · cos x = 7² + 10² – 12²
140 · cos x = 49 + 100 – 144
cos x = (149 – 144) / 140
x = 87.95 ≈ 88°
Then the correct option is C.
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