B

9000039304

Level: 
B
Find the focus length \(f\) as a function of the other variables from the following equation relating this distance with object and image distances \(a\) and \(a'\). \[ \frac{1} {f} = \frac{1} {a} + \frac{1} {a'} \]
\(f = \frac{aa'} {a+a'}\)
\(f = \frac{a-a'} {a+a'}\)
\(f = a + a'\)
\(f = \frac{a} {a'}\)

9000045708

Level: 
B
Given a regular hexagon with the side \(a\), find the radius \(\rho \) of the circle inscribed to this hexagon.
\(\rho = \frac{a} {2\cdot \mathop{\mathrm{tg}}\nolimits 30^{\circ }}\)
\(\rho = 2a\cdot \mathop{\mathrm{tg}}\nolimits 30^{\circ }\)
\(\rho = \frac{2a} {\mathop{\mathrm{tg}}\nolimits 30^{\circ }}\)
\(\rho = 2a\cdot \mathop{\mathrm{tg}}\nolimits 60^{\circ }\)

9000038910

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

9000039305

Level: 
B
Find \(m_{1}\) as a function of the other variables from the following mixing equation. \[ w_{1}m_{1} + w_{2}m_{2} = w_{3}m_{3} \]
\(m_{1} = \frac{w_{3}m_{3}-w_{2}m_{2}} {w_{1}} \)
\(m_{1} = \frac{w_{3}m_{3}w_{2}m_{2}} {w_{1}} \)
\(m_{1} = \frac{w_{3}m_{3}+w_{2}m_{2}} {w_{1}} \)
\(m_{1} = \frac{w_{2}m_{2}-w_{3}m_{3}} {w_{1}} \)

9000046405

Level: 
B
A circle is circumscribed to the regular octagon. The perimeter of the octagon is \(16\, \mathrm{cm}\). Find the radius of the circle and round the result to two decimal places. (The regular octagon is a polygon which has eight sides of equal length. The perimeter of the octagon is the sum of the length of all eight sides.) Circle circumscribed to the regular octagon.
\(2.61\, \mathrm{cm}\)
\(1.08\, \mathrm{cm}\)
\(1.41\, \mathrm{cm}\)

9000046408

Level: 
B
Consider a cone of base radius \(r\) and a special shape: the shape is such that the volume of the cone is related to the base radius by the formula \(V =\pi r^{3}\). Find the angle between the side of the cone and the base. Round your answer to two decimal places.
\(71.57^{\circ }\)
\(45^{\circ }\)
\(63.43^{\circ }\)

9000045702

Level: 
B
Given a right triangle \(ABC\) (see the picture). Find the valid relation between the angle \(\alpha \) and the sides of the triangle.
\(\mathop{\mathrm{tg}}\nolimits \alpha = \frac{a} {c}\)
\(\sin \alpha = \frac{a} {c}\)
\(\cos \alpha = \frac{b} {a}\)
\(\mathop{\mathrm{cotg}}\nolimits \alpha = \frac{b} {a}\)

9000045710

Level: 
B
Find the length \(l\) of a latitude at \(50^{\circ }\) N. (Use \(R\) for the radius of the Earth.)
\(l = 2\pi R\cos 50^{\circ }\)
\(l = 2\pi R\sin 50^{\circ }\)
\(l = 2\pi R\mathop{\mathrm{tg}}\nolimits 50^{\circ }\)
\(l = 2\pi R\mathop{\mathrm{cotg}}\nolimits 50^{\circ }\)

9000045703

Level: 
B
Given a right triangle \(ABC\) with the right angle at $C$ and an altitude $v$ (see the picture). Find the valid relation between the angle \(\alpha \) and the lengths in the triangle.
\(\sin \alpha = \frac{v} {b}\)
\(\sin \alpha = \frac{v} {c}\)
\(\sin \alpha = \frac{a} {v}\)
\(\sin \alpha = \frac{c} {a}\)