If $\theta$ is an acute angle of a right triangle where $\sin \theta = x/2$, compute the value of $\sin 2\theta$ in terms of $x$.

If $\theta$ is an acute angle of a right triangle where $\sin \theta = x/2$, compute the value of $\sin 2\theta$ in terms of $x$.

A. $\dfrac{x}{\sqrt{4 - x^2}}$ C. $2x \sqrt{4 - x^2}$
B. $\frac{1}{2}x \sqrt{4 - x^2}$ D. $\dfrac{\sqrt{4 - x^2}}{x}$

From the given right triangle what is the value of $3 \sin^2 \varphi \, \sec \varphi$ in terms of $x$.

From the given right triangle what is the value of $3 \sin^2 \varphi \, \sec \varphi$ in terms of $x$.

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A. $\dfrac{x}{\sqrt{x^2 + 9}}$ C. $\dfrac{x^2 + 9}{\sqrt{x^2 - 9}}$
B. $\dfrac{9}{\sqrt{x^2 + 9}}$ D. $\dfrac{x^2}{\sqrt{x^2 + 9}}$