The sum of the other two angles is less than 79.19°. Then the largest angle is D.
What is the law of cosine?
Let there is triangle ABC such that |AB| = a unit, |AC| = b units, and |BC| = c units and the internal angle A is of θ degrees, then we have:
a² + b² -2ab cos θ = c²
Where (c is an opposite side to angle A)
Then the angle D will be
12² + 10² - 2 x 12 x 10 x cos D = 17²
144 + 100 - 240 x cos D = 289
- 240 x cos D = 45
cos D = - 0.1875
D = 100.80°
Then the sum of the other two angles is less than 79.19°.
Thus, the correct option is C.
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