Labeling the angles of a triangle as A, B, and C and the lengths of the corresponding opposite sides as a, b and c. Given b=7 and A=30°. If the triangle is identified and unique, the value of a satisfies.

A) a<3.5 B) a>3.5 C) 3.5<a<8 D) a>8 E) none

3 answers

Draw altitude from C to side c
sin 30 = its length /7
but sin 30 = 1/2
so it is 3.5
EVERY other line from C to c is longer than that
so
a > 3.5
If a > 3.5 then ABC is not unique, as there are two solutions, one with C obtuse (a > 7.5) and the other with B obtuse (a < 3.5)

The only unique solution I see is where a = 3.5
Oops - typo. I should have said
two solutions, one with C obtuse (c > 7cosA) and the other with B obtuse (c < 7cosA)