A5 1)
cos - sin*ctg =cos - sin *cos/sin =cos - cos= 1
B1
(tg^2 -sin^2)/(ctg^2 - cos^2 ) - (tg^6 - 7)=
=sin^2(1/cos^2 - 1) / cos^2 (1/sin^2 - 1 ) - (tg^6 - 7)=
=tg^2*(1-cos^2/cos^2 ) / (1-sin^2/sin^2 ) - (tg^6 - 7)=
=tg^2*(sin^2/cos^2 ) / (cos^2/sin^2 ) - (tg^6 - 7)=
=tg^2*tg^2 / ctg^2 - (tg^6 - 7)= tg^6 - tg^6 +7 = 7
B2 cos - sin = 1.2
(cos + sin)^2 - 5sin*cos=cos^2 +2cos*sin +cos^2 - 5 sin*cos=
=cos^2 -3cos*sin +cos^2 = cos^2 -2cos*sin +cos^2 -cos*sin=
=(cos - sin )^2 -cos*sin=1.2^2 -cos*sin=1.44 -cos*sin
C1 Докажите тождество
1/(1+tg^2) + 1/(1+ctg^2) =1
1/(1+tg^2) + 1/(1+1/tg^2) =1
1/(1+tg^2) + tg^2/(1+tg^2) =1
(1+ tg^2)/(1+tg^2) =1
1=1