题目内容：

求值：

cos40°+sin50°(1+ 3 tan10°)

sin70° 1+sin50°

．

优质解答

cos40°+sin50°(1+ 3 tan10°)

sin70° 1+sin50°

=

cos40°+sin50°(1+ 3 sin10° cos10° )

cos20° 1+cos40°

=
=

cos40°+cos40°( 2sin(10°+30°) cos10° )

2 cos220°

=

cos40°+1

2 cos220°

=

2

．