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`        Which rational number should be the correct value of √3cot20 - 4 cos20 `
one year ago

Arun
22281 Points
```							√3*cot 20 - 4*cos 20= √3*cos 20/sin 20 - 4*cos 20= (√3*cos 20 - 4*cos 20*sin 20)//sin 20= (√3*cos 20 - 2*2*cos 20*sin 20)//sin 20= {√3*cos 20 - 2*sin (2*20)}//sin 20= {√3*cos 20 - 2*sin 40}//sin 20                    {since sin 2x = 2*sin x*cosx}= {2*sin 60*cos 20 - 2*sin 40}//sin 20           {since sin 60 = √3/2}= {sin 80 + sin 40 - 2*sin 40}//sin 20              {since 2*sin A*cos B = sin (A + B) + sin (A - B)}= {sin 80 - sin 40}//sin 20                      = {2*cos 60*sin 20}/sin 20                     {since sin A - sin B = 2 * sin (A - B)/2 *cos (A + B)/2}= 2*cos 60                             = 2 * 1/2                                                  {since cos 60 = 1/2]= 1
```
one year ago
Saurabh Koranglekar
2933 Points
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one year 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