Sign of Trigonometric Ratios in Different Quadrants
The value of ...
Question
The value of cotπ20cot3π20cot5π20cot7π20cot9π20 is
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Solution
Given cotπ20cot3π20cot5π20cot7π20cot9π20=(cotπ20cot9π20)cotπ4(cot3π20cot7π20)=(cotπ20cot(π2−π20))(cot3π20cot(π2−3π20))=(cotπ20tanπ20)(cot3π20tan3π20)=1