Question
If $2\sin^2 \theta + 3sin \theta = 0$, find the permissible values of cosθ.

Answer

$2 \sin { }^2 \theta+3 \sin \theta=0$
$\therefore \sin \theta(2 \sin \theta+3)=0$
$\therefore \sin \theta=0 \text { or } \sin \theta=\frac{-3}{2}$
$\text { Since }-1 \leq \sin \theta \leq 1,$
$\sin \theta=0$
$\sqrt{1-\cos ^2 \theta}=0 \ldots\left[\because \sin ^2 \theta=1-\cos ^2 \theta\right]$
$\therefore 1-\cos ^2 \theta=0$
$\therefore \cos ^2 \theta=1$
$\therefore \cos \theta= \pm 1 \ldots[\because-1 \leq \cos \theta \leq 1]$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

Define a relation R on the set N of natural number by R = $\{$(x, y): y = x + 5}, x is a natural number less than 4, $\text{x, y}\in\text{N}\}$
Depict this relationship using:
  1. Roster form.
  2. An arrow diagram. Write down the domain and range or R.
Find the square root of the following complex numbers:
$1-\text{i}$
In a hostel, 25 students take tea, 20 students take coffee, 15 students take milk, 10 students take both tea and coffee, 8 students take both milk and coffee. None of them take tea and milk both and everyone takes atleast one beverage, find the total number of students in the hostel.
Solve the following system of equations in R.
x + 5 > 2(x + 1), 2 - x < 3(x + 2)
A bag contains 3 red and 5 white balls. Two balls are drawn at random one after the other without replacement. Find the probability that both the balls are white.
If n A.M.s are inserted between two numbers, prove that the sum of the means equidistant from the beginning and the end is constant.
Find the centre and radius of each of the following circles:
$4 x^2+4 y^2-24 x-8 y-24=0$
If A, B, C, D be the angles of a cyclic quadrilateral, take in order, proved that:
$\cos(180^\circ-\text{A})+\cos(180^\circ+\text{B})+\cos(180^\circ+\text{C})-\sin(90^\circ+\text{D})=0$
Find the probability that in a random arrangement of the letters of the word 'UNIVERSITY', the two I's do not come together.
Express the following in the form of $a + ib, a, b \in R, i = \sqrt{-1}.$ State the values of $a$ and $b: (1 + i)(1 – i)-1$