If sin20 ° cos50 ° = a, then sin50 ° sin70 ° is equal to

If sin20 ° cos50 ° = a, then sin50 ° sin70 ° is equal to

sin50°sin70°=cos20°sin50°
cos20°sin50°-sin20°cos50°=sin（50°-20°）=sin30°=1/2
therefore
sin50°sin70°=a+1/2

Simplification: ① cos 20 ° cos 40 ° cos 60 ° cos 80 ° and ② sin 20 ° + cos 50 ° + sin 30 ° sin 70 ° Simplification: ① cos 20 ° cos 40 ° cos 60 ° cos 80 ° and ② sin 20 ° + cos 50 ° + sin 30 ° sin 70 °

Cos 20 ° cos 40 ° cos 60 ° cos 80 ° = (sin 20 cos 40 ° cos 60 ° cos 80 °) = (sin 20 ° cos 40 ° cos 60 ° cos 80 °) = (sin 20 ° cos 40 ° cos 60 ° cos 80 °) / 2 sin 20 ° (2 times angle formula) = (sin 80 ° cos 60 ° cos 80 °) / 4sin 20 °

Simplification (tan10 degree - radical 3) * cos10 degree / sin50 degree

（tan10°－√3）cos10°/sin50°
＝（sin10°/cos10°－√3）cos10°/sin50°
＝（sin10°－√3cos10°）/sin50°
＝2［（1/2）sin10°－（√3/2）cos10°］/sin50°
＝2（sin10°cos60°－cos10°sin60°）/sin50°
＝2sin（10°－60°）/sin50°
＝－2

Simplification: (tan10 ° − 3)•cos10° sin50°．

(tan10°−
3)•cos10°
sin50°
=(sin100−
3cos100)•cos100
cos100•sin500
=2(1
2sin100−
Three
2cos100)
sin500
=2(sin100cos600−cos100sin600)
sin500
=2sin(−500)
sin500=-2

Simplification (Tan 10 degree - radical 3) times sin 50 fractions cos 10 degree (with process)

（tan10°-√3）×cos10°/sin50° =（sin10°/cos10°-√3）×cos10°/sin50° =（sin10°-√3cos10°）/sin50° =2（1/2×sin10°-√3/2×cos10°）/sin50° =2（cos60°sin10°-sin60°cos10°）/sin50° =2×sin...

(tan10 ° - radical 3) × cos10 ° / sin50 °

=[sin10°/cos10°－√3]cos10°/sin50°
=[sin10°－√3cos10°]/sin50°
=2[sin10°cos60°－cos10°sin60°]/sin50°
=2sin(10°－60°)/sin50°
=－2

Calculation: sin20 ° - sin40 ° / cos20 ° - cos40 ° Sin20 ° - sin40 ° are molecules Cos 20 ° to Cos 40 ° is the denominator

sin20°-sin40°/cos20°-cos40°
=sin20°-sin40°/sin70°-sin50°
=2sin[(20-40)/2]cos[(20+40)/2]/2sin[(70-50)/2]cos[(70+50)/2]
=sin(-10)cos30/sin10cos60
=-sin10cos30/sin10cos60
=-sin60/cos60
=--tan60
=-√3

The value of sin20 ° cos40 ° + cos20 ° sin40 ° is equal to () A. 1 Four B. Three Two C. 1 Two D. Three Four

sin20°cos40°+cos20°sin40°
=sin60°
=
Three
Two
Therefore, B

Simplify sin20 ° cos40 ° + cos20 ° sin40 °=______ .

sin20°cos40°+cos20°sin40°
=sin（20°+40°）
=sin60°=
Three
2，
So the answer is:
Three
2．

(1-cos20 / sin20 radical 3) sin40

(1-cos20)/sin20-√3
=(1-cos20-√3sin20)/sin20
=(1-2sin(20+30))/sin20
=(1-2sin50)/sin20
[(1-cos20)/sin20-√3]*sin40
=[(1-2sin50)/sin20]*2sin20cos20
=2[(1-2cos40)cos20]
=2 [cos20-2cos40cos20]
=2cos20-4[cos(40+20)+cos(40-20)]/2
=-2cos60
=-1