Sin(-13π/4)=-sin(13π/4)=-sin(8π/4+5π/4)=-sin 5π/4=-sin(4π/4+π/4)=
= -sin (π+π/4)= sinπ/4=√2/2
tg(-19π/6)=-tg19π/6=-tg(18π/6+π/6)=-tg(3π+π/6)=-tgπ/6=-√3/3
cos13π/4=cos(12π/4+π/4)=cos(2π+π+π/4)=cos(π+π/4) =- cos(π/4)=-√2/2
сtg7π/4=ctg(4π/4+3π/4)=ctg3π/4=ctg(π-π/4)=-ctgπ/4=-1
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sint=-√2/2 t=(-1)^k*arcsin(-√2/2)+πk=(-1)^k*(-π/4)+πk k∈Z
cost=0 t=π/2+πk k∈Z
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вычисляем учитывая нечетнось синуса и косинуса и 2π - период косинуса
=(-sint)/(-tgt)-cost=sint*cost/sint-cost=0
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