-- This is a right triangle. We know that because that little box
is drawn at the right angle (C).
-- Since it's a right triangle, we can use the side lengths
in trigonometry equations.
-- The drawing tells us the length of the side OPPOSITE
the unknown angle (the 3), and also the length of the side
ADJACENT to the unknown angle (the 6).
-- While we're saying "opposite" and "adjacent" to ourselves,
that reminds us that the tangent of an angle is the quotient of
(opposite side) / (adjacent side).
-- So we know that the tangent of the unknown angle is (3/6) or (1/2) or 0.5 .
-- With our calculator, our slide rule, our general knowledge, or the
tables in our Handbook of Chemistry and Physics, we look up to
find what angle has a tangent of 0.5 . It's 26.57° .
