What degree of COS is equal to 0.943

What degree of COS is equal to 0.943

19 degrees 26 minutes 18.1 seconds

sin20°)^2+(sin40°)^2-2sin20°*sin40°*cos120° =(sin120°)^2

Solution (1) (sin20 °) ^ 2 + (cos50 °) ^ 2 + sin20 ° * cos50 ° = (sin20 °) ^ = (sin20 °) ^ 2 + (sin40 °) ^ 2-2sin20 ° * sin40 ° * cos120 ° = (sin120 °)

2cos20 ° (- sin20 ° / sin40 °), I want to explain in detail,

2cos20°(-sin20° / sin40°),
=-2sin20°cos20°/sin40°
=-sin40°/sin40°
=-1
formula
sin2a=2sinacosa

Seeking {(1-cos20) / sin20 - √ 3} * sin40 without looking up the table
It is helpful for the responder to give an accurate answer

(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]
=2cos20-2[cos(40+20)+cos(40-20)]
=-2cos60
=-1