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Dasha010100
@Dasha010100
October 2021
1
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Только 29 задание. Тригонометрия
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sedinalana
Verified answer
Tg2a=-0,5
cos²2a=1;(1+tg²2a)=1:(1+1/4)=4/5
cos2a=2/√5
sin2a=-√(1-cos²2a)=-√(1-4/5)=-1/√5
sin4a=2sin2acos2a=2*(-1/√5)*2/√5=-4/5
cos4a=cos²2a-sin²2a=4/5-1/5=3/5
1-cos²4a=sin²4a
sin8a=2sin4acos4a=2*(-4/5)*3/5=-24/25
(sin8a+2sin4a)/(1-cos²4a)=(-24/25+2*(-4/5)):16/25=(-24/25-8/5):16/25=
=(-24-40)/25*25/16=-64/16=-4
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Answers & Comments
Verified answer
Tg2a=-0,5cos²2a=1;(1+tg²2a)=1:(1+1/4)=4/5
cos2a=2/√5
sin2a=-√(1-cos²2a)=-√(1-4/5)=-1/√5
sin4a=2sin2acos2a=2*(-1/√5)*2/√5=-4/5
cos4a=cos²2a-sin²2a=4/5-1/5=3/5
1-cos²4a=sin²4a
sin8a=2sin4acos4a=2*(-4/5)*3/5=-24/25
(sin8a+2sin4a)/(1-cos²4a)=(-24/25+2*(-4/5)):16/25=(-24/25-8/5):16/25=
=(-24-40)/25*25/16=-64/16=-4