Sin6thita+cos6thita=1-3sin2thita×cos2thita
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from LHS
sin^6 ¢ + cos^6¢
= ( sin²¢ )³ + (cos²¢)³
°•° we know that a³ + b³ = ( a + b ) (a² + b² - ab)
using this .
we get
= (sin²¢ + cos²¢ ) ( sin⁴¢ + cos⁴¢ - sin²¢ cos²¢ )
= 1 { ( sin²¢ )² + ( cos²¢ )² - sin²¢ cos²¢ }
[using rule a² + b² = ( a + b)²-2ab]
= { (sin²¢ + cos²¢ )² - 2sin²¢ cos²¢ - sin²¢ cos²¢
= 1 - 3sin²¢ cos²¢ prooved ♻
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