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Sagot :
Certainly! Let's prove the given trigonometric identity step by step:
[tex]\[ \tan \frac{x}{2} + \cot \frac{x}{2} = 2 \csc x \][/tex]
1. Express [tex]\(\tan\frac{x}{2}\)[/tex] and [tex]\(\cot\frac{x}{2}\)[/tex] using sine and cosine:
[tex]\[ \tan\frac{x}{2} = \frac{\sin\frac{x}{2}}{\cos\frac{x}{2}} \][/tex]
[tex]\[ \cot\frac{x}{2} = \frac{\cos\frac{x}{2}}{\sin\frac{x}{2}} \][/tex]
2. Combine [tex]\(\tan\frac{x}{2}\)[/tex] and [tex]\(\cot\frac{x}{2}\)[/tex] over a common denominator:
[tex]\[ \tan\frac{x}{2} + \cot\frac{x}{2} = \frac{\sin\frac{x}{2}}{\cos\frac{x}{2}} + \frac{\cos\frac{x}{2}}{\sin\frac{x}{2}} \][/tex]
[tex]\[ = \frac{\sin^2\frac{x}{2} + \cos^2\frac{x}{2}}{\sin\frac{x}{2} \cos\frac{x}{2}} \][/tex]
3. Use the Pythagorean identity:
[tex]\[ \sin^2\frac{x}{2} + \cos^2\frac{x}{2} = 1 \][/tex]
Therefore:
[tex]\[ \tan\frac{x}{2} + \cot\frac{x}{2} = \frac{1}{\sin\frac{x}{2} \cos\frac{x}{2}} \][/tex]
4. Recall the double-angle identity for sine:
[tex]\[ \sin x = 2 \sin\frac{x}{2} \cos\frac{x}{2} \][/tex]
This means:
[tex]\[ \sin\frac{x}{2} \cos\frac{x}{2} = \frac{\sin x}{2} \][/tex]
5. Substitute this back into the expression:
[tex]\[ \tan\frac{x}{2} + \cot\frac{x}{2} = \frac{1}{\frac{\sin x}{2}} = \frac{2}{\sin x} \][/tex]
6. Use the definition of cosecant:
[tex]\[ \csc x = \frac{1}{\sin x} \][/tex]
So:
[tex]\[ \frac{2}{\sin x} = 2 \csc x \][/tex]
Therefore:
[tex]\[ \tan\frac{x}{2} + \cot\frac{x}{2} = 2 \csc x \][/tex]
This completes our proof! The identity [tex]\(\tan\frac{x}{2} + \cot\frac{x}{2} = 2 \csc x\)[/tex] has been successfully proven.
[tex]\[ \tan \frac{x}{2} + \cot \frac{x}{2} = 2 \csc x \][/tex]
1. Express [tex]\(\tan\frac{x}{2}\)[/tex] and [tex]\(\cot\frac{x}{2}\)[/tex] using sine and cosine:
[tex]\[ \tan\frac{x}{2} = \frac{\sin\frac{x}{2}}{\cos\frac{x}{2}} \][/tex]
[tex]\[ \cot\frac{x}{2} = \frac{\cos\frac{x}{2}}{\sin\frac{x}{2}} \][/tex]
2. Combine [tex]\(\tan\frac{x}{2}\)[/tex] and [tex]\(\cot\frac{x}{2}\)[/tex] over a common denominator:
[tex]\[ \tan\frac{x}{2} + \cot\frac{x}{2} = \frac{\sin\frac{x}{2}}{\cos\frac{x}{2}} + \frac{\cos\frac{x}{2}}{\sin\frac{x}{2}} \][/tex]
[tex]\[ = \frac{\sin^2\frac{x}{2} + \cos^2\frac{x}{2}}{\sin\frac{x}{2} \cos\frac{x}{2}} \][/tex]
3. Use the Pythagorean identity:
[tex]\[ \sin^2\frac{x}{2} + \cos^2\frac{x}{2} = 1 \][/tex]
Therefore:
[tex]\[ \tan\frac{x}{2} + \cot\frac{x}{2} = \frac{1}{\sin\frac{x}{2} \cos\frac{x}{2}} \][/tex]
4. Recall the double-angle identity for sine:
[tex]\[ \sin x = 2 \sin\frac{x}{2} \cos\frac{x}{2} \][/tex]
This means:
[tex]\[ \sin\frac{x}{2} \cos\frac{x}{2} = \frac{\sin x}{2} \][/tex]
5. Substitute this back into the expression:
[tex]\[ \tan\frac{x}{2} + \cot\frac{x}{2} = \frac{1}{\frac{\sin x}{2}} = \frac{2}{\sin x} \][/tex]
6. Use the definition of cosecant:
[tex]\[ \csc x = \frac{1}{\sin x} \][/tex]
So:
[tex]\[ \frac{2}{\sin x} = 2 \csc x \][/tex]
Therefore:
[tex]\[ \tan\frac{x}{2} + \cot\frac{x}{2} = 2 \csc x \][/tex]
This completes our proof! The identity [tex]\(\tan\frac{x}{2} + \cot\frac{x}{2} = 2 \csc x\)[/tex] has been successfully proven.
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