F`(x)=(1/3ctg15x)`*(15x)~+(√3)`=-1/3sin²15x)*15+0=-5/sin²15x
F`(π/4)=-5/sin²(15π/4)=-5/sin²(4π-π/4)=-5/sin²(-π/4)=-5:(√2/2)²=
=-5:(1/2)=-10
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Sкр.=ПR^2=1, Sш.=4ПR^2=4*1=4
А2+а4=14
а7=а3+12
1)а1+д+а1+3д=14
2а1+4д=14
а1+2д=7
2)а7-а3=12
а1+6д-(а1+2д)=12
а1+6д-а1-2д=12
4д=12
д=3
3)а1+6=7
а1=1
<span>(sin a+1)(sin a-1)=(sina)</span><span>²-1=-(cosa)</span><span>²</span>
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</span>(sina)²+(cosa)²=1<span>
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