Answer:
2.9 units
Explanation:
Here the leg lengths are x and 7.7 and the one given angle is 21 degrees.
Think: which trig function incorporates both the length of the side opposite the 21 degree angle (x) and the vertical side (7.7)? It's the tangent function:
tan Ф = opp / adj
To be clear: the side adjacent (next to) the 21 degree angle is 7.7 units in length and the side opposite this angle is x.
Then we have tan 21 degrees = opp / adj = x / 7.7
and so 7.7(tan 21 degrees) = 7.7(03839) = 2.96 or (to one decimal place) 2.9