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kimcuong09
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Bài 1 : rút gọn :
a, A = ( 1 + 2sin A .cos A) / ( cos^2 A - sin^2 A )
b, B = ( 1 + tg^2 A )(1 - sin^2 A) - ( 1 + cotg^2 A )( 1 - cos^2 A )
Bài 2 chứng minh
a, 1 + tg^2 A = 1 / ( cos^2 A )
b, cotg^2 A - cos^2 A = cotg^2 A . cos^2 A
c, 1 + cotg^2 A = 1 / sin^2 A
d, ( 1 + cos A ) / sin A = sin A / ( 1 - cos^2 A )
giúp tui vs tui đang cần gấp![Eek! :eek: :eek:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
a, A = ( 1 + 2sin A .cos A) / ( cos^2 A - sin^2 A )
b, B = ( 1 + tg^2 A )(1 - sin^2 A) - ( 1 + cotg^2 A )( 1 - cos^2 A )
Bài 2 chứng minh
a, 1 + tg^2 A = 1 / ( cos^2 A )
b, cotg^2 A - cos^2 A = cotg^2 A . cos^2 A
c, 1 + cotg^2 A = 1 / sin^2 A
d, ( 1 + cos A ) / sin A = sin A / ( 1 - cos^2 A )
giúp tui vs tui đang cần gấp