铁肩担风雨
春芽
共回答了10个问题采纳率:100% 举报
BC=AC-AB=(2,-4)-(2,3)=(0,-7),
|BC|=7;
(AB+AC)*BC
={(2,3)+(2,-4)})*(0,-7)
=(4,-1)*(0,-7)
=7
sina/cosa=tana=3
3cosa=sina
(sina)^2+(cosa)^2=1
10(cosa)^2=1
(cosa)^2=1/10
sin^2a-2sinacosa
=(tan^2a-2tana)*cos^2a
=3/10
直线BC的方程已知B(5,-1)C(3,3) 两点式
k=(y2-y1)/(x2-x1),代入点斜式,得y=k·(x-x1)+y1最后得
2x+y-9=0;
BC边上的高:K1*K2=-1
得k2=-1/2 点 C(3,3)代人
x-2y-1=0;
BC边上的中线:
B(5,-1)C(3,3) 中点=(4,1)
中点(4,1)与A(1,0),两点式得
x-3y+1=0;
f(x)=1+2sinxcosx+2cos^2x
=2+sin2x+2cos^2x-1
=2+sin2x+cos2x
=√2(sin(2x+π/4)) +2
最小正周期 T=2π/2=π
2kπ-π/2
1年前
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