Question

高一数学题一道，急求答案！！！！！！！

(1+sin4A+cos4A)/(1+sin4A-cos4A)=
A.cotA B.cot2A C.tanA D.tan2A

Answer 1

原式=（sin²2a+cos²2a+2sin2acos2a+cos²2a-sin²2a)/
(sin²2a+cos²2a+2sin2acos2a-cos²2a+sin²2a)
=[(sin2a+cos2a)²+(cos2a+sin2a)(cos2a-sin2a)]/
[(sin2a+cos2a)²-(cos2a+sin2a)(cos2a-sin2a)]
=cos2a/sin2a
=cot2a
选B。

Answer 2

你好，满意请采纳哦！
选择D
(1 + sin 4 a - cos 4 a) / (1 + sin 4 a + cos 4 a)
= (1 - cos 4 a + sin 4 a) / (1 + cos 4 a + sin 4 a)
= (2 sin^2 2 a + 2 sin 2 a cos 2 a)/ (2 cos^2 2 a + 2 sin 2 a cos 2 a)
= [2 (sin 2 a) (sin 2 a + cos 2 a)]/ [2 (cos 2 a) (cos 2 a + sin 2 a)]
= sin 2 a / cos 2 a
= tan 2 a .