高一必修4三角函数sin420*cos750+sin(-330)*cos(-660)tan675+tan765-tan(-330)+tan(-690)sin(25π/6)+cos(25π/3)+tan(-25π/4)2.已知sin(π+α)=-1/2 计算(1)sin(5π-α) (2)sin(π/2+α) (3)cos(α-3π/2) (4)tan(π/2-α)

sin420*cos750+sin(-330)*cos(-660)
=sin60cos30+sin30cos60
=sin(60+30)
=sin90
=1
tan675+tan765-tan(-330)+tan(-690)
=-tan45+tan45-tan30+tan30
=0
sin(25π/6)+cos(25π/3)+tan(-25π/4)
=sin(π/6)+cos(π/3)+tan(-π/4)
=1/2+1/2-1
=0
2.已知sin(π+α)=-1/2 则-sina=-1/2 sina=1/2
cosa=（根号3）/2或者cosa=-（根号3）/2
(1)sin(5π-α)
=sina=1/2

(2)sin(π/2+α)
=cosa
=（根号3）/2或者-（根号3）/2
(3)cos(α-3π/2)
=cos(α+π/2)
=-sin α
=-1/2
(4)tan(π/2-α)
=cotα
=（根号3）
或者-（根号3）

sin420*cos750+sin(-330)*cos(-660)sin和cos周期是360,所以通过加或减360的整数倍原式=sin60*cos30+sin30*cos60=sin(60+30)=sin90=1tan675+tan765-tan(-330)+tan(-690)tan周期是180,所以也是加或减180的整数倍原式=t...