There are two solutions because the rocket first reaches the height of 980 cm as it's going up at 1 second, then it reaches that height again as it's coming down at 2 seconds.
<span>Complements sum to 90 degrees. If 1 and 2 are complements, and m1=35 deg, then m2 =90-35 = 55 degrees.
Now if 2 and 3 are complements, and m2= 55 deg., then m3= 90 - 55 = 35 degrees.</span>