cosα(2secα+tanα)(secα-2tanα)+3tanα 请帮忙化简
cosα(2secα+tanα)(secα-2tanα)+3tanα
=cosα(2secα*secα-4secα*tanα+secα*tanα-2tanα*tanα)+3tanα
=cosα[2(secα*secα-tanα*tanα)-4secα*tanα+secα*tanα]+3tanα
=cosα(2-3secα*tanα)+3tanα
=2cosα-3cosα*secα*tanα+3tanα
=2cosα-3tanα+3tanα
=2cosα