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`        If sec(theta+alpha) + sec(theta-alpha)=2sectheta prove that cos theta= 2^1/2 cosalpha/2`
11 months ago

Arun
22612 Points
```							Dear student  sec(θ+α)+sec(θ−α)=2sec(θ) can be written as1cos(θ+α)+1cos(θ−α)=2cosθor cos(θ+α)+cos(θ−α)cos(θ+α)cos(θ−α)=2cos(θ)or2×2cosθcosαcos(θ+α+θ−α)+cos(θ+α−θ+α)=2cosθor 2cosθcosαcos2θ+cos2α=1cosθor 2cos2θcosα=cos2θ+cos2αor 2cos2θcosα=2cos2θ−1+2cos2α−1or 2cos2θ(cosα−1)=2cos2α−2or cos2θ=cos2α−1cosα−1=cosα+1or cos2θ=2cos2(α2)and cosθ=√2cos(α2)Hope it helps
```
11 months ago
Saurabh Koranglekar
3161 Points
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11 months 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