Find all solutions to the equation [tex]$3 \sin (5t) = 2$[/tex] in the interval [tex]$0 \leq t \leq \frac{\pi}{2}$[/tex] radians.

A. [tex]0.1459, 1.4026[/tex]
B. [tex]0.1459, 0.4824, 1.4026[/tex]
C. [tex]0.1682, 1.0884, 1.425[/tex]
D. [tex]0.1682, 1.425[/tex]



Answer :

To find all solutions to the equation [tex]\( 3 \sin(5t) = 2 \)[/tex] within the interval [tex]\( 0 \leq t \leq \frac{\pi}{2} \)[/tex], we will follow these steps:

1. Isolate the sine function:
[tex]\[ \sin(5t) = \frac{2}{3} \][/tex]

2. Find the general solution for [tex]\( \sin(5t) \)[/tex] when [tex]\( \sin(5t) = \frac{2}{3} \)[/tex]:
- To find [tex]\(5t\)[/tex], we need to use the inverse sine function (arcsine).
- Let [tex]\( x = 5t \)[/tex]. Then, [tex]\( \sin(x) = \frac{2}{3} \)[/tex].
- The primary solutions for [tex]\( x \)[/tex] in the interval [tex]\([0, \pi]\)[/tex] are: [tex]\( x = \arcsin\left(\frac{2}{3}\right) \)[/tex] and [tex]\( x = \pi - \arcsin\left(\frac{2}{3}\right) \)[/tex].

3. Calculate numeric values:
- Note that [tex]\(\arcsin\left(\frac{2}{3}\right)\)[/tex] gives us an angle in radians whose sine is [tex]\( \frac{2}{3} \)[/tex].
- Let's denote [tex]\( \arcsin\left(\frac{2}{3}\right) = \theta \)[/tex].

4. Find [tex]\( t_1 \)[/tex] and [tex]\( t_2 \)[/tex]:

Solving for [tex]\( x = 5t \)[/tex]:
- [tex]\( 5t_1 = \theta \)[/tex] [tex]\(\Rightarrow t_1 = \frac{\theta}{5} \)[/tex]
- [tex]\( 5t_2 = \pi - \theta \)[/tex] [tex]\(\Rightarrow t_2 = \frac{\pi - \theta}{5} \)[/tex]

By knowing that:
[tex]\[ \theta \approx 0.7297 \, \text{radians} \][/tex]

- [tex]\( t_1 = \frac{0.7297}{5} \approx 0.1459 \)[/tex]
- [tex]\( t_2 = \frac{\pi - 0.7297}{5} \approx 0.4824 \)[/tex]

These give us the two solutions within the interval [tex]\( 0 \leq t \leq \frac{\pi}{2} \)[/tex].

5. Verify if there are any other solutions within the interval:

Since [tex]\( 5t \)[/tex] must be in [tex]\([0, \pi]\)[/tex]:
[tex]\[ 0 \leq 5t \leq \pi \Rightarrow 0 \leq t \leq \frac{\pi}{5} \approx 0 \leq t \leq 0.6283 \][/tex]

Hence, in the interval [tex]\( 0 \leq t \leq \frac{\pi}{2} \)[/tex], the previously calculated [tex]\( t_1 \approx 0.1459 \)[/tex] and [tex]\( t_2 \approx 0.4824 \)[/tex] are the only solutions.

Thus, the correct answer is:
b) [tex]\( 0.1459, 0.4824 \)[/tex]