Draw a line straight down the middle of the triangle.
the answer is 0.921.
Apply the trig identity: cos (a + b) = cos a.cos b - sin a.sin b
<span><span>cos<span>(75)</span></span>=<span>cos<span>(30+45)</span></span>=<span>cos30</span>⋅<span>cos45</span>−<span>sin30</span>⋅<span>sin45</span><span>=
0.921
</span></span>
The sum of 18 and 3 is 21