C

1003032507

Level: 
C
Express \( v_1 \) from the formula \( v=\frac{v_1v_2(d_1+d_2 )}{d_1v_2+d_2v_1} \).
\( v_1=\frac{vd_1 v_2}{v_2d_1+v_2d_2-vd_2} \)
\( v_1=\frac{vv_2 d_1}{vd_2-v_2d_1-v_2d_2} \)
\( v_1=\frac{vv_2(d_1+d_2)}{d_1v_2+d_2 v} \)
\( v_1=\frac{v(d_1v_2+d_2 v_1 )}{v_2 (d_1+d_2 )} \)

1003032506

Level: 
C
In a parallel circuit the total resistance \( R \) of three components with the resistances \( R_1 \), \( R_2 \), \( R_3 \) is given by the formula \( \frac1R=\frac1{R_1}+\frac1{R_2}+\frac1{R_3} \). Express \( R_1 \) from this formula.
\( R_1=\frac{RR_2R_3}{R_2R_3-R(R_2+R_3)} \)
\( R_1=\frac{R-R_2-R_3}{RR_2R_3} \)
\( R_1=R-\frac{R_2R_3}{R_2+R_3} \)
\( R_1=\frac{R_2R_3-R(R_2+R_3)}{RR_2R_3} \)

1003086108

Level: 
C
The solution set of the equation \( 1 + \sin x \cdot \cos 2x = \sin x + \cos 2x \) for \( x\in\mathbb{R} \) is:
\( \bigcup\limits_{k\in\mathbb{Z}}\left\{\frac{\pi}2+2k\pi;k\pi\right\} \)
\( \bigcup\limits_{k\in\mathbb{Z}}\left\{\frac{\pi}2+2k\pi\right\} \)
\( \bigcup\limits_{k\in\mathbb{Z}}\left\{k\pi\right\} \)
\( \bigcup\limits_{k\in\mathbb{Z}}\left\{2k\pi\right\} \)

1003086107

Level: 
C
The solution set of the equation \( 2\mathrm{tg}^2x + 4\cos^2x = 7 \) for \( x\in\mathbb{R} \) is:
\( \bigcup\limits_{k\in\mathbb{Z}}\left\{\frac{\pi}3+k\pi;\frac{2\pi}3+k\pi\right\} \)
\( \bigcup\limits_{k\in\mathbb{Z}}\left\{\frac{\pi}3+2k\pi;\frac{2\pi}3+2k\pi\right\} \)
\( \bigcup\limits_{k\in\mathbb{Z}}\left\{\frac{\pi}3+k\pi\right\} \)
\( \bigcup\limits_{k\in\mathbb{Z}}\left\{\frac{2\pi}3+k\pi\right\} \)
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