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Question : 120 of 150
Marks:
+1,
-0
Solution:
Given,
cot‌70°+4‌cos‌70° =+4‌cos‌70° =| cos‌70°+4‌sin‌70°‌cos‌70° |
| sin‌70° |
=| cos‌70°+2‌sin(180°−40°) |
| sin‌70° |
=| cos(90°−20°)+2‌sin‌40° |
| sin‌70° |
=| sin‌20°+sin‌40°+sin‌40° |
| sin‌70° |
=| 2‌sin‌30°‌cos‌10°+sin‌40° |
| sin‌70° |
=| 2‌sin‌30°‌cos(90°−80°)+sin‌40° |
| sin‌70° |
=| sin‌80°+sin‌40° |
| sin‌70° |
=| 2‌sin‌60°‌cos‌20° |
| sin‌70° |
=| 2()‌sin‌70° |
| sin‌70° |
=√3
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