1.

Write the value of tan10° tan 20° tan 70° tan 80°.

Answer»

tan10° tan 20° tan 70° tan 80°

= cot(90° − 10° ) cot(90° − 20° ) tan70° tan80° 

= cot80° cot70° tan70° tan80°

= 1/tan 80° × 1/tan 70° × tan 70° × tan 80° 

= 1



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