сократите дробь cos40 градусов-------------------------- = cos20 - sin20

Question

сократите дробь



cos40 градусов

-------------------------- =

cos20 - sin20

Answer 1

cos40/(cos20-sin20)=(cos^2(20)-sin^2(20))/(cos20-sin20)=(cos20-sin20)(cos20+sin20)/(cos20-sin20)=cos20+sin20

Answer 2

sin40=2*sin20*cos20

2*sin20*cos20/sin20=2cos20