Hi Ibrahim. Since sin (theta)= 3/5, and we are dealing with the first quadrant, the answer is positive, since all trig functions are positive in quadrant one.
Now we look at the formula for the double angle. Cos (2 theta) =
two possible formulas, but we pick 1-2 sin squared A, because we are given sin to begin with. The other formula is = to 2 cos squared A-1, but we are not given cos in the question, but we are given sin.
Therefore, 1- 2 sin squared A = 1- 2(3/5)squared = 1- 2(9/25) = 1-18/25, = 7/25. That is the answer.
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