X=900/100-5
x=4
900/(4+5)=100
Качество конечно не очень
428060;428100; 428000;430000;
30,000;26,000;25,6000;25,6100;25,6070;
Сos²a=1:(1+tg²a)=1:(1+9/16=1:25/16=16/25
cosa=-4/5
sina=√(1-cos²a)=√(1-16/25)=√9/25=3/5
cos(π/4+a)=cosπ/4*cosa-sinπ/4*sina=√2/2*(-4/5)-√2/2*3/5=
=√2/2*(-4/5-3/5)=√2/2*(-7/5)=-7√2/10