Using a trigonometric identity, since in the first quadrant and in the third quadrant the sine and the cosine have the same sign, [tex]\sin{2\theta}[/tex] is always positive.
It is given by:
[tex]\sin{2\theta} = 2\sin{\theta}\cos{\theta}[/tex]
In the first quadrant(0° < θ < 90°) and in the third(180° < θ < 270°), the sine and the cosine have the same sign, hence the multiplication is positive and [tex]\sin{2\theta}[/tex] is always positive.
More can be learned about trigonometric identities at https://brainly.com/question/24496175
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