Question

数学必修四P28页第6，7题答案

Answer 1

6(1) sin186°=sin(180°+16°)=-sin16°<0
(2)tan505°=tan(360°+145°)=tan145°=tan(180°-45°)= -tan45°<0
(3)sin7.6π=sin(8π-0.4π)=-sin0.4π=-sin72°<0
(4)tan(-23π/4)=-tan23π/4=-tan(6π-π/4)=-tan(-π/4)=tanπ/4>0
(5)cos940°=cos(1080°-140°)=cos(-140°)=cos140°<0
(6)cos(-59π/17)=cos59π/17=cos(3π+8π/17)=-cos8π/17<0
7.(1)tan125°sin273°因为tan125°=tan(180°-55°)=-tan55°<0sin273°=sin(360°-87°)=-sin87°<0
所以.tan125°sin273°>0

(2)tan108°/cos305°
因为tan108°=tan(180°-72°)=-tan72°<0cos305°=sin(360°-55°)=-sin55°<0
所以tan108°/cos305°>0
(3)sin5π/4 cos4π/5 tan11π/6容易算出sin5π/4<0 cos4π/5<0 tan11π/6<0sin5π/4cos4π/5tan11π/6<0
(4)(cos5π/6× tan11π/6)/(sin2π/3)容易算出sin5π/6>0 cos4π/5<0 sin2π/3>0(cos5π/6× tan11π/6)/(sin2π/3)<0

Answer 2

把题写出来

Answer 3

小学的么？？？