\
The distance from the Sun to Earth is approximately .
The distance from the Sun to Mercury is approximately .
The elongation angle is the angle formed between the line of sight from Earth to the Sun and the line of sight from Earth to Mercury .
Consider the distance between the earth and mercury as .
Draw a diagram for the situation:
\Observe the figure:
\ .
Apply the Law of Sines for triangle :
and
.
.
.
\
Apply the Law of Sines for triangle for
:
\
Apply the Law of Sines for triangle for
.
Thus, Possible distances between Earth and Mercury are approximately or
.
\
Possible distances between Earth and Mercury are approximately or
.