Answer:
Tan20°×tan40°×Tan60°=3
Tan60×tan40°tan20°)
√3((2tan20°)/(1-tan²20))tan20
√3(2tan²20/(1-tan²20°)
2√3((sin²20/cos²20)/((cos²20-sin²20)/cos²20))
2√3(sin²20/(cos²20-sin²20))
2√3(sin²20/(1-2sin²20)
2√3sin²20/2cos²40
√3
