Задача 47234 Вычеслите: cos70cos10+sin70sin10 ------------------------------...

vk537255449

2020-04-15 18:36:10

Вычеслите:
cos70cos10+sin70sin10
------------------------------ =
sin50cos10+cos50sin10

sova

2020-04-15 18:43:29

[r]cos α *cos β +sin α *sin β =cos( α - β )[/r]

cos70 ° cos10 ° +sin70 ° sin10 ° =cos(70 ° - 10 ° )=cos60 °

[r] sin α *cos β +cos α *sin β =sin( α + β )[/r]

sin50 ° cos10 ° +cos50 ° sin10 ° =sin60 °


сtg60 ° =sqrt(3)/3 - о т в е т

kodzimageniy

2020-04-15 18:44:32

cos70cos10+sin70sin10=cos(70-10) cos60 ____________________________ =_____ = ctg60= 1/sqrt(3)=sqrt(3)/3
sin50cos10+cos50sin10=sin(50+10) sin60
[ sin/cos=tg; cos/sin=ctg ]