tan 20° x tan 40° x tan 80° = tan 60°
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Answer:Given, tan 20 * tan 40 * tan 80
= tan 40 * tan 80 * tan 20
= [{sin 40 * sin 80}/{cos 40 * cos 80}] *(sin 20/cos 20)
= [{2 * sin 40 * sin 80}/{2 * cos 40 * cos 80}] *(sin 20/cos 20)
= [{cos 40 - cos 120}/{cos 120 + cos 40}] *(sin 20/cos 20)
= [{cos 40 - cos (90 + 30)}/{cos (90 + 30) + cos 40}] *(sin 20/cos 20)
= [{cos 40 + sin30}/{-sin30 + cos 40}] *(sin 20/cos 20)
= [{(2 * cos 40 + 1)/2}/{(-1 + cos 40)/2}] *(sin 20/cos 20)
= [{2 * cos 40 + 1}/{-1 + cos 40}] *(sin 20/cos 20)
= [{2 * cos 40 * sin 20 + sin 20}/{-cos 20 + cos 40 * cos 20}]
= (sin 60 - sin 20 + sin 20)/(-cos 20 + cos 60 + cos 20)
= sin 60/cos 60
= tan 60
So, tan 20 * tan 40 * tan 80 = tan 60
Step-by-step explanation:
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