The triangle formed is an isosceles triangle assuming that the orbit is circular. Get the measure of the third angle:
180 - 2(2) = 176°
Next, use the cosine law to solve for the distance of the star from the Earth
d = sqrt[ 186² + 186² - 2 x 186 x 186 cos 176° ]
d = 371.77
The distance of the start from Earth is 371.77 millions miles.