Sin^2a+cos^2a=1
sinA=корень из 1-соs^2a
sinA=корень из 1-0,81
sinA=корень из 0,19
(x-4)^2-x^2=12
x^2-8x+4-x^2=12
-8x+4=12
-8x=8
x=-1
25y^2-1-(5y-2)^2=0
25y^2-1-(25y^2-20y+4=0
25y^2-1-25y^2+20y-4=0
-1+20y-4=0
-5+20y=0
20y=5
y=4
2*(4-12a+9a²)-18a²+16a=8-24a<u>+18a²-18a²</u>+16a=8-8a=8*(1-a)=8*(1-(-0,2)=8*1,2=9,6
Cosa=2/5
sina=√(1-cos²a)=√(1-4/25)=√(21/25)=√21/5
sin2a=2sinacosa=2*2/5*√21/5=4√21/25
cos2a=cos²a-sin²a=4/25-21/25=-17/25
tga=sina/cosa=√21/5:2/5=√21/5*5/2=√21/2
cos(π/3+a)=cosπ/3cosa-sinπ/3sina=1/2*2/5-√3/2*√21/5=1/5-3√7/10=(2-3√7)/10
sin(a-π/6)=sinacosπ/6-cosasinπ/6=√21/5*√3/2-2/5*1/2=3√7/10-1/5=(3√7-2)/10