Question

Find the indicated angle or side. Give an exact answer. Find the measure of angle A in degrees.

Answer 1

Step-by-step explanation:

law of cosine :

c² = a² + b² - 2ab×cos(C)

with c being the side opposite of C.

so, in our case

3² = 3² + 3²×3 - 2×3×3×sqrt(3)×cos(A)

0 = 3²×3 - 18×sqrt(3)×cos(A)

27 = 18×sqrt(3)×cos(A)

cos(A) = 27/(18×sqrt(3)) = 3/(2×sqrt(3)) =

= 0.866025404...

A = 30°

FYI : since it is an isoceles triangle, C = A = 30°.

and therefore B = 180 - 30 - 30 = 120°.

as the sum of all angles in a triangle is always 180°.