Помогите!20 БАЛЛОВ!!!!!Болел!
a)sin2t/cost - sint
б)sin40/cos20
в)sin 6t/cos^2 3t
г)cos 80/cos40+sin40
д)2 sin15 cos15
е)(cos75-sin75)^2
a)sin2t/cost - sint
б)sin40/cos20
в)sin 6t/cos^2 3t
г)cos 80/cos40+sin40
д)2 sin15 cos15
е)(cos75-sin75)^2
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Answers & Comments
Б)sin40/cos20=2sin20cos20/cos20=2sin20
В)2sin (3t)
Г)cos 2*40 / (cos 40 +sin 40) = (cos^2 40-sin^2 40)/ (cos 40 +sin 40)=
= (cos 40 +sin 40) (cos 40 -sin 40) /(cos 40 +sin 40) = cos 40-sin 40
Д) Формула двойного угла: )
2 Sin 15' Cos 15' = sin 30 = 0,5
Е) (cos75-sin75)^2=cos75^2-2*cos75*sin75+sin75^2=1-2cos75*sin75=1-sin150=1-sin(180-30)=1-sin30=1-0,5=0,5
Sin2t/cost-sint=2sinTcosT/cosT - sinT=2sinT-sinT=sinT