1)tg(arctg3/4+arctg1/7)=tgπ/4
tg(arctg3/4+arctg1/7)=1
tg(arctg3/4+arctg1/7)=(tg(arctg3/4)+tg(arctg1/7))/(1-tg(arctg3/4)*tg(arctg1/7))=
=(3/4+1/7)/(1-3/4*1/7)=25/28:(1-3/28)=25/28:25/28=1
1=1⇒arctg3/4+arctg1/7=π/4
2)sin(arcsin0,8+arccos0,8)=sinπ/2
sin(arcsin0,8+arccos0,8)=1
sin(arcsin0,8)cos(arccos0,8)+cos(arcsin0,8)sin(arccosa)=
=0,8*0,8+√1-0,64*√1-0,64=0,64+0,6*0,6=0,64+0,36=1
1=1⇒arcsin0,8+arccos0,8=π/2