Помогите плиз заранее большое спасибо

cos(-45)=cos45=√2/2     sin405=sin(405-360)=sin45=√2/2 cos900=cos(900-720)=cos180= -1 tg(-π/3)=-tgπ/3=-1/2  ctg(-7π/3)=-ctg7π/3=-ctg(7π/3-6π/3)=--ctgπ/3=-√3/3 (√2/2*√2/2+1)/(1/2*√3/3)=(3/2)/(√3/6)=3*6/(2√3)=9/√3=9√3/3=3√3 ----------------------------- 1-1/2+1/4.....  b1=1   q=-1/2 s=b1/(1-q)=1/(1+1/2)= 1*2/3=2/3