Question

25. Prove that cot 6* cot 42° cot 66° cot 78° = 1​

Answer 1

Answer:

use formula cot a . cot (60°-a). cot(60°+a)= cot3a

Explanation:

here multiply and divide it by cot54°.(using above formula)

then , cot18°. cot 42°. cot 78/ cot54°(" " " " " )

so we get cot 54°/cot 54°=1

Answer 2

Explanation:

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