化简
-sin a+sin a-(-sin a)-(-sin a)
=2sin a
证明
1.原式=sin a*cos b+cos a*sin b/cos a*cos b
分子分母同除以cos a*cos b
=tan a+tan b
2.原式=(sin a*cos b+cos a*sin b)(cos a*coa b+sin a*sin b)
将式子乘开后合并同类项
=sin a*cos a+sin b*cos
化简
-sin a+sin a-(-sin a)-(-sin a)
=2sin a
证明
1.原式=sin a*cos b+cos a*sin b/cos a*cos b
分子分母同除以cos a*cos b
=tan a+tan b
2.原式=(sin a*cos b+cos a*sin b)(cos a*coa b+sin a*sin b)
将式子乘开后合并同类项
=sin a*cos a+sin b*cos