Question

in triangle abc , ab = 6root3 cm , Ac = 12 cm and bc = 6 cm . find the measure of angle A

Answer 1

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Answer 2

Answer:

The measure of angle A is 30°.

Step-by-step explanation:

Law of cosine

$\cos A=\frac{b^2+c^2-a^2}{2bc}$

It is given that in triangle ABC , AB = 6√3 cm , AC = 12 cm and BC = 6 cm .

$c=6\sqrt{3}$

$b=12$

$a=6$

$\cos A=\frac{(12)^2+(6\sqrt{3})^2-(6)^2}{2(12)(6\sqrt{3})}$

$\cos A=0.866$

$A=cos^{-1}(0.866)$

$A=30^{\circ}$

Therefore the measure of angle A is 30°.