Answer: option d. the argument is valid by the law of detachment.
The law of detachment consists in make a conlcusion in this way:
Premise 1) a => b
Premise 2) a is true
Conclusion: Then, b is true
Note: the order of the premises 1 and 2 does not modifiy the argument.
IN this case:
Premise 1) angle > 90 => obtuse
Premise 2) angle = 102 [i.e. it is true that angle > 90]]
Conclusion: it is true that angle is obtuse
The value of the side c will be 5.56 cm and angle C is 32.49° and angle B is 42.51°.
<h3>What is law of cosine?</h3>
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:
a² + b² – 2ab cos C = c²
Given triangle ABC, A = 105°, a = 10 cm, b = 7 cm.
Then we have
7² + c² – (2 · 7 · c) cos 105° = 10²
c² + 3.62c – 51 = 0
On solving, we have
c = 5.56
Then the angle C will be
10² + 7² – 2 · 7 · 10 · cos C = 5.56²
149 – 140 cos C = 30.91
cos C = 0.8435
C = 32.49°
We know that
∠A + ∠B + ∠C = 180°
105° + ∠B + 32.49° = 180°
∠B = 42.51°
Learn more about law of cosines here:
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The remaining co-ords are (1,2) and (5,4).
