求助三道高一数学三角函数题1、用tan(alpha)表示tan(alpha/2)2、化简：sin(50)(1+根号3tan(10))（角度）3、求证：(1-tan^2(alpha/2))/(1+tan^2(alpha/2))=cos(alpha)详细过程,谢谢
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1tan(alpha)=2tan(alpha)/(1+tan^2(alpha/2))
22sin(50)(1/2+根号3/2tan(10))
=2sin(50)/cos10(1/2cos10+根号3/2son(10))
=2sin(50)/cos10*sin40
=2sin(50)cos50/cos10
=sin100/cos10=1
3：(1-tan^2(alpha/2))/(1+tan^2(alpha/2))=
切化弦 太不好输入 讲就下思路 通分 运用二倍角就可以了