化简 sin(π/2+a)cos(π/2-a)/cos(3π/2-a)sin(3π/2+a)

sin(π/2+a)cos(π/2-a)/cos(3π/2-a)sin(3π/2+a)
=(cosasina)/(-sinα*-cosα)
=1
sin25π/6+cos25π/3+tan(-25π/4)
=sinπ/6+cosπ/3+tan(-π/4)
=1/2+1/2-1
=0
sin（2kπ+α）=sinα
cos（2kπ+α）=cosα
tan（2kπ+α）=tanα
cot（2kπ+α）=cotα
sec（2kπ+α）=secα
csc（2kπ+α）=cscα
sin（π+α）=－sinα
cos（π+α）=－cosα
tan（π+α）=tanα
cot（π+α）=cotα
sec(π+α)=-secα
csc(π+α)=-cscα
sin（－α）=－sinα
cos（－α）=cosα
tan（－α）=－tanα
cot（－α）=－cotα
sec(-α)=secα
csc(-α)=-cscα
sin（π－α）=sinα
cos（π－α）=-cosα
tan（π－α）=－tanα
cot（π－α）=－cotα
sec(π-α)=-secα
csc(π-α)=cscα
sin（α-π）=－sinα
cos（α-π）=－cosα
tan（α-π）=tanα
cot（α-π）=cotα
sec(α-π)=-secα
csc(α-π)=－cscα
sin（2π－α）=－sinα
cos（2π－α）=cosα
tan（2π－α）=－tanα
cot（2π－α）=－cotα
sec(2π-α)=secα
csc(2π-α)=-cscα
sin（π/2+α）=cosα
cos（π/2+α）=－sinα
tan（π/2+α）=－cotα
cot（π/2+α）=－tanα
sec(π/2+α)=-cscα
csc(π/2+α)=secα
sin（π/2－α）=cosα
cos（π/2－α）=sinα
tan（π/2－α）=cotα
cot（π/2－α）=tanα
sec(π/2-α)=cscα
csc(π/2-α)=secα
sin（3π/2+α）=－cosα
cos（3π/2+α）=sinα
tan（3π/2+α）=－cotα
cot（3π/2+α）=－tanα

手机看不清，没办法了

sin(π/2+a)cos(π/2-a)/cos(3π/2-a)sin(3π/2+a)
=cosasina/(-sina*-cosa)
=cosasina/(sinacosa)
=1
2) sin25π/6+cos25π/3+tan(-25π/4)
=sin(4π+π/6)+cos(8π+π/3)+tan(4π-25π/4)
=sinπ/6+cosπ/3+tan(-π/4)
=sinπ/6+cosπ/3+tan(-π/4)
=1/2+1/2-tanπ/4
=1-1
=0

1)sinacosa/(-cosa)(-sina)=1
2)sin(pi/6) cos(pi/3) tan(-pi/4)=1/2 1/2-1=0