B

9000046509

Level: 
B
Identify the optimal first step convenient to solve the following trigonometric equation. Do not consider the step which is possible but does not help to solve the equation. \[ 2\cos ^{2}x =\sin x + 1 \]
\(2 - 2\sin ^{2}x =\sin x + 1\)
substitution \( \sin x + 1 = z\)
substitution \( \cos x = z\)
\(2\cos ^{2}x = \sqrt{1 -\sin ^{2 } x} + 1\)

9000046406

Level: 
B
Find the area of the regular octagon of the perimeter \(16\, \mathrm{cm}\). Round the result to two decimal places. (The regular octagon is a polygon which has eight sides of equal length, see the picture. The perimeter of the octagon is the sum of the length of all eight sides.)
\(19.31\, \mathrm{cm}^{2}\)
\(3.31\, \mathrm{cm}^{2}\)
\(20.88\, \mathrm{cm}^{2}\)

9000039005

Level: 
B
Find all the values of \(x\) for which the following expression is positive. \[ \frac{2x - 3} {7 - 3x} \]
\(x\in \left (\frac{3} {2}; \frac{7} {3}\right )\)
\(x\in \left (\frac{3} {2};+\infty \right )\)
\(x\in \left (\frac{7} {3};+\infty \right )\)
\(x\in (0;+\infty )\)

9000046409

Level: 
B
The base of a pyramid is a square with the side of \(2\, \mathrm{cm}\). The height of the pyramid is \(4\, \mathrm{cm}\). Find the angle between the lateral side of the pyramid and the base. Round your result to two decimal places.
\(75.96^{\circ }\)
\(70.52^{\circ }\)
\(79.98^{\circ }\)

9000039101

Level: 
B
Find the polar form of the complex number \(z=\frac{\mathrm{i}^{14}-1} {\mathrm{i}^{9}+1} \).
\(\sqrt{2}\left (\cos \frac{3\pi } {4} + \mathrm{i}\sin \frac{3\pi } {4}\right )\)
\(\sqrt{2}\left (\cos \frac{5\pi } {4} + \mathrm{i}\sin \frac{5\pi } {4}\right )\)
\(\sqrt{2}\left (\cos \frac{\pi }{4} + \mathrm{i}\sin \frac{\pi }{4}\right )\)
\(\sqrt{2}\left (\cos \frac{7\pi } {4} + \mathrm{i}\sin \frac{7\pi } {4}\right )\)

9000039106

Level: 
B
Find the value of the parameter \(a\) which guarantees that the quadratic equation \[ x^{2} + 2ax + a = 0 \] has a pair of complex conjugate solutions with a nonzero imaginary part.
\(a\in (0;1)\)
\(a\in [ 0;1] \)
\(a\in (-\infty ;0)\cup (1;\infty )\)
Such an \(a\) does not exist

9000038909

Level: 
B
Consider the function \(f\colon y =\sin \left (\frac{x} {2} + \frac{\pi } {2}\right )\). In the following list identify the function which has the same graph as the graph of the function \(f\).
\(g\colon y =\cos \frac{x} {2} \)
\(k\colon y =\cos \left (\frac{x} {2} + \frac{\pi } {2}\right )\)
\(b\colon y =\cos \left (\frac{x} {2} - \frac{\pi } {2}\right )\)
\(h\colon y =\cos \left (\frac{x} {2} -\pi \right )\)
\(m\colon y =\cos 2x\)