Sin(180°) = 0
sec(0°)=1
4(0)+2(1)=2
Recall that for
, we have

Replace
with
and we get

Lastly, multiply this by
, so that

Similar, they have the same angles but different sides.
Congruent is same sides, same angles.
The other 2 just ignore.
The answer is similar.
The coefficient of -7x is -7, since -7 is the number being multiplied by x.
Similarly, the coefficient of 9/4y is 9/4, since it is the number being multiplied by y.
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