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Solve the following question Prove that- b² cos2A - a² cos2B = b²-a²

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2 years ago

Arun
25768 Points
```							Dear Sanjay First use the formula cos 2A = 1 - 2sin²A (1 - 2sin²A)/a² - (1 - 2sin²B)/b² = 1/a² - 2sin²A/a² - 1/b² + 2sin²B/b² = 1/a² - 1/b² + 2sin²B/b² - 2sin²A/a² Now think of the law of sines in a triangle sinA/a = sinB/b sin²A/a² = sin²B/b² Hence 2sin²B/b² - 2sin²A/a² = 0 So Cos2A/a² - cos2B/b² = 1/a² - 1/b²
```
2 years ago
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### Course Features

• 31 Video Lectures
• Revision Notes
• Test paper with Video Solution
• Mind Map
• Study Planner
• NCERT Solutions
• Discussion Forum
• Previous Year Exam Questions