Math, asked by dprashant15, 1 year ago

Prove that cos10.cos20-cos80cos70=√3/2

Answers

Answered by GENIUS1223
0

Answer:

Step-by-step explanation:

 (cos10° + sin20°) / (cos20° - sin10°) 

= tan60° * (cos60°/sin60°) * [(cos10° + sin20°) / (cos20° - sin10°)] 

= tan60° * [(2cos60° cos10° + 2cos60° sin20°) / (2sin60°cos20° - 2sin60° sin10°)] 

= √3 * [(cos70° + cos50° + sin80° - sin40°) / (sin80° + sin40° - cos50° + cos70°)] 

= √3 * [(cos70° + cos50° + sin80° - cos50°) / (sin80° + cos50° - cos50° + cos70°)] 

.......................................... sin40° = cos50°] 

= √3 * [(cos70° + sin80°) / (sin80° + cos70°)] 

= √3 

= 1.732050808.

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