Question

高一数学。帮下忙

Answer 1

追答

Answer 2

2)原式=sin10cos55-cos10sin55=sin(10-55)=-sin45=-√2/2

14)

1:a1+a4=3,a6=5
2a1+3d=3,a1+5d=5
解得a1=0,d=1
an=n-1
2:a2=2,a9=30
a1+d=2 ,a1+8d=30
解得a1=-2,d=4
S10=10*(-2)+1/2*10*9*4=160
S10=160
3:b2=6,b4=18
b2=b1q=6,b4=b1q^3=18
解得;q=√3或q=-√3
b1=2√3或b1=-2√3
b6=2√3*(√3)^5=54
15)

a^2+b^2+√2ab=c^2
a^2+b^2-c^2=-√2ab
cosC=(a^2+b^2-c^2)/2ab=-√2ab/2ab=-√22
C=3π/4

sinA=2sinBcosC
sin(B+C)=2sinBcosC
sinBcosC+cosBsinC=2sinBcosC
sinBcosC-cosBsinC=0
sin(B-C)=0
B=C
三角形ABC是等腰三角形
16)

1)sina+cosa=1/2
(sina+cosa)^2=1/4
1+2sinacosa=1/4
sin2a=-3/4
2)tana=1/7,tanb=3/4

tan(a+b)=(tana+tanb)/(1-tanatanb0
=(1/7+3/4)/(1-1/7*3/4)
=1
a+b=π/4

3)cos(a+b)=-5/13,sinb=3/5

sin(a+b)=12/13,cosb=4/5
sina=sin[(a+b)-b]=sin(a+b)cosb-cos(a+b)sinb
=12/13*4/5+5/13*3/5
=63/65

追问

谢咯

Answer 3

百度一下你就知道

Answer 4

兄弟

追答

上作业帮啊