化简 sinα的三次方sin3α+cos αde

5个回答

sin³αsin3α+cos³αcos3α=sin³α(3sinα-4sin³α)+cos³α(4cos³α-3cosα)=3(sin^4α-cos^4α)-4(sin^6α-cos^6α)=3(sin²α+cos²α)(sin²α-cos²α)-4(sin...