Solution: Given that $Z=\left(i^{25}\right)^{3}$ $\begin{array}{l} =\dot{i}^{75} \\ =\mathrm{i}^{74} \cdot \mathrm{i} \\ =\left(\mathrm{i}^{2}\right)^{37} \cdot \mathrm{i} \\ =(-1)^{37} \cdot...
Find the modulus and argument of the following complex numbers and hence express each of them in the polar form:
(i) $sin 120^o – i cos 120^o$
(ii) -16 / (1 + i√3)
Solution: It is known to us that the polar form of a complex number $Z=x+i$ iy is given by $Z=|Z|(\cos \theta+i \sin \theta)$ In which, $\begin{array}{l} \left.|Z|=\text { modulus of complex number...
Find the modulus and argument of the following complex numbers and hence express each of them in the polar form:
(i) 1/(1 + i)
(ii) (1 + 2i) / (1 – 3i)
Solution: It is known to us that the polar form of a complex number $Z=x+i$ iy is given by $Z=|Z|(\cos \theta+i \sin \theta)$ In which, $\begin{array}{l} \left.|Z|=\text { modulus of complex number...
Find the modulus and argument of the following complex numbers and hence express each of them in the polar form:
(i) 1 + i
(ii) √3 + i
Solution: It is known to us that the polar form of a complex number $Z=x+i$ iy is given by $Z=|Z|(\cos \theta+i \sin \theta)$ In which, $\begin{array}{l} \left.|Z|=\text { modulus of complex number...
If $z_{1}, z_{2}$ and $z_{3}, z_{4}$ are two pairs of conjugate complex numbers, prove that arg $\left(z_{1} / z_{4}\right)+\arg \left(z_{2} / z_{3}\right)=0$
Solution: Given that $\begin{array}{l} z_{1}=\bar{z}_{2} \\ z_{3}=\bar{z}_{4} \end{array}$ It is known that $\arg \left(\mathrm{z}_{1} / \mathrm{z}_{2}\right)=\arg \left(\mathrm{z}_{1}\right)-\arg...
Express $\sin \pi / 5+i(1-\cos \pi / 5)$ in polar form.
Solution: Given that $Z=\sin \pi / 5+i(1-\cos \pi / 5)$ Using the formula, $\begin{array}{l} \sin 2 \theta=2 \sin \theta \cos \theta \\ 1-\cos 2 \theta=2 \sin ^{2} \theta \end{array}$ Therefore,...
A metallic right circular cone 20 cm high and whose vertical angle is 60° is cut into two parts at the middle of its height by a plane parallel to its base. If the frustum so obtained is drawn into a wire of diameter 1/16 cm, find the length of the wire.
Solution: Let $A B C$ be the metallic cone, $DECB$ is the required frustum Let the two radii of the frustum be$\mathrm{DO}^{\prime}=\mathrm{r}_{2}$ and $\mathrm{BO}=\mathrm{r}_{1}$From $\triangle...
A container, opened from the top and made up of a metal sheet, is in the form of a frustum of a cone of height 16 cm with radii of its lower and upper ends as 8 cm and 20 cm, respectively. Find the cost of the milk which can completely fill the container, at the rate of Rs. 20 per litre. Also find the cost of metal sheet used to make the container, if it costs Rs. 8 per 100 cm2.
Given, r1 = 20 cm, r2 = 8 cm and h = 16 cm \[\therefore Volume\text{ }of\text{ }the\text{ }frustum\text{ }=\text{ }\left( \right)\times \pi \times h\left( r12+r22+r1r2 \right)\] It is given that...
A fez, the cap used by the Turks, is shaped like the frustum of a cone (see Fig.). If its radius on the open side is 10 cm, radius at the upper base is 4 cm and its slant height is 15 cm, find the area of material used for making it.
Given, For the lower roundabout end, span $(r_1)$ = 10 cm For the upper roundabout end, span $(r_2)$ = 4 cm Inclination tallness (l) of frustum = 15 cm Presently, The space of material to be...
The slant height of a frustum of a cone is 4 cm and the perimeters (circumference) of its circular ends are 18 cm and 6 cm. Find the surface area of the frustum.
Given, Inclination tallness (l) = 4 cm Perimeter of upper roundabout finish of the frustum = 18 cm \[\therefore 2\pi r_1\text{ }=\text{ }18\] Or on the other hand, $r_1$ = 9/π Likewise, periphery of...
A drinking glass is in the shape of a frustum of a cone of height 14 cm. The diameters of its two circular ends are 4 cm and 2 cm. Find the capacity of the glass.
Sweep $(r_1)$ of the upper base = 4/2 = 2 cm Sweep $(r_2)$ of lower the base = 2/2 = 1 cm Tallness = 14 cm Presently, Capacity of glass = Volume of frustum of cone Thus, Capacity of glass = \[\left(...