Schmidt Hardy
06/11/2023 · Junior High School
3. If \( \cos x=\frac{3}{5} \), \( x \) lies in the second quadrant, find the values of \( \sin x \), \( \tan x, \sec x \) 4. Prove that \( \frac{\sin 5 x+\sin 3 x}{\cos 5 x+\cos 3 x}=\tan 4 x \) 8. d) The value of \( f^{2 a} \) is b) Find the muliplicative inverse of \( 1- \) in atib form 6.i) If \( (x+1, y-2)=(3,1) \), find the values of \( x \) and \( y \) ii) Find the domain and range of the function \( \sin x \) (i) Solve the inequality \( x+\frac{x}{2}+\frac{x}{3}<10+\frac{x}{6} \) ii) Mark the solution in a number line
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### Problem 3
Given \( \cos x = \frac{3}{5} \) and \( x \) lies in the second quadrant, we need to find \( \sin x \), \( \tan x \), and \( \sec x \).
1. **Finding \( \sin x \)**:
Using the Pythagorean identity:
\[
\sin^2 x + \cos^2 x = 1
\]
Substituting \( \cos x \):
\[
\sin^2 x + \left(\frac{3}{5}\right)^2 = 1
\]
\[
\sin^2 x + \frac{9}{25} = 1
\]
\[
\sin^2 x = 1 - \frac{9}{25} = \frac{25}{25} - \frac{9}{25} = \frac{16}{25}
\]
\[
\sin x = \pm \sqrt{\frac{16}{25}} = \pm \frac{4}{5}
\]
Since \( x \) is in the second quadrant, \( \sin x \) is positive:
\[
\sin x = \frac{4}{5}
\]
2. **Finding \( \tan x \)**:
\[
\tan x = \frac{\sin x}{\cos x} = \frac{\frac{4}{5}}{\frac{3}{5}} = \frac{4}{3}
\]
3. **Finding \( \sec x \)**:
\[
\sec x = \frac{1}{\cos x} = \frac{1}{\frac{3}{5}} = \frac{5}{3}
\]
Thus, the values are:
- \( \sin x = \frac{4}{5} \)
- \( \tan x = \frac{4}{3} \)
- \( \sec x = \frac{5}{3} \)
---
### Problem 4
We need to prove that:
\[
\frac{\sin 5x + \sin 3x}{\cos 5x + \cos 3x} = \tan 4x
\]
Using the sum-to-product identities:
\[
\sin A + \sin B = 2 \sin\left(\frac{A+B}{2}\right) \cos\left(\frac{A-B}{2}\right)
\]
\[
\cos A + \cos B = 2 \cos\left(\frac{A+B}{2}\right) \cos\left(\frac{A-B}{2}\right)
\]
Let \( A = 5x \) and \( B = 3x \):
\[
\sin 5x + \sin 3x = 2 \sin\left(4x\right) \cos\left(x\right)
\]
\[
\cos 5x + \cos 3x = 2 \cos\left(4x\right) \cos\left(x\right)
\]
Now substituting these into the left-hand side:
\[
\frac{2 \sin(4x) \cos(x)}{2 \cos(4x) \cos(x)} = \frac{\sin(4x)}{\cos(4x)} = \tan(4x)
\]
Thus, we have proved:
\[
\frac{\sin 5x + \sin 3x}{\cos 5x + \cos 3x} = \tan 4x
\]
---
### Problem 6
**i)** Given \( (x+1, y-2) = (3, 1) \), we can set up the equations:
\[
x + 1 = 3 \quad \Rightarrow \quad x = 2
\]
\[
y - 2 = 1 \quad \Rightarrow \quad y = 3
\]
Thus, \( x = 2 \) and \( y = 3 \).
**ii)** The domain and range of the function \( \sin x \):
- **Domain**: All real numbers, \( (-\infty, \infty) \)
- **Range**: \( [-1, 1] \)
---
### Problem 8
**d)** The value of \( f^{2a} \) is not specified in the question. Please provide more context or details.
**b)** To find the multiplicative inverse of \( 1 - \) in "atib" form, we need clarification on what "atib" refers to
Quick Answer
- \( \sin x = \frac{4}{5} \), \( \tan x = \frac{4}{3} \), \( \sec x = \frac{5}{3} \)
- The equation is proved: \( \frac{\sin 5x + \sin 3x}{\cos 5x + \cos 3x} = \tan 4x \)
- \( x = 2 \), \( y = 3 \)
- Domain of \( \sin x \): \( (-\infty, \infty) \), Range: \( [-1, 1] \)
- The value of \( f^{2a} \) is not specified. The multiplicative inverse of \( 1 - \) in "atib" form is not clear.
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