1) Найти значения: sina,cosa,tga, если tga=0,4; Π
tga=sina/cosa
sina/cosa=0.4
sina=0.4*cosa
√(1-cos²a)=0.4*cosa
1-cos²a=0.16cos²a
1.16cos²a=1
cos²a=1/1.16=25/29
cosa=+-5/√29
Πcosa=-5/√29
sina=0.4*cosa=-5*0.4/√29=-2/√29
2) Вычислите: (sin68cos38-cos128cos68)/(sin^2 79+sin^2 169)
cos128=cos(π/2+38)=-sin38
sin169=sin(π/2+79)=cos²79
(sin68cos38+sin38cos68)/(sin² 79+cos²79)= (sin68cos38+sin38cos68)/1=sin(38+68)=sin(106)=sin(
π/2+16)=cos16