EDUCACene,excelleeos 40%,cos20Â°sin 20

1.	EDUCACene,excelleeos 40%,cos20Â°sin 20
Answer» calculate without using trigonometric table 2cos40 - cos20 = cos40 + (cos40 - cos20) = cos40 - 2sin((40+20)/2)sin((40-20)/2) = cos40 - 2sin30sin10 = sin(90-40) - sin10 = sin50 - sin10 = 2sin((50-10)/2)cos((50+10)/2)=2sin20√3/2=√3sin20√3*sin20 / sin20 =√3

Answer»

calculate without using trigonometric table

2*cos40 - cos20 = cos40 + (cos40 - cos20) = cos40 - 2*sin((40+20)/2)*sin((40-20)/2) = cos40 - 2*sin30*sin10 = sin(90-40) - sin10 = sin50 - sin10 = 2*sin((50-10)/2)*cos((50+10)/2)=2*sin20*√3/2=√3*sin20√3*sin20 / sin20 =√3

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EDUCACene,excelleeos 40%,cos20Â°sin 20

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