Answer: Choice A) 4, 3, 5, 1, 2
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Explanation:
Since tan(x) = sin(x)/cos(x) is a known and widely used trig identity, this must mean step 4 goes first.
The answer is between choice A and choice B.
The question is now: What is the correct second step?
It's either step 3 (choice A) or step 5 (choice B)
It turns out that step 3 is the correct statement after step 4. The sin(2x) breaks up into 2sin(x)cos(x), while the cos(2x) breaks up into cos^2(x)-sin^2(x). There are three different variations for the cos(2x) and this just happens to be one of them.
So we can rule out choice B and go with choice A as the final answer.
