tan(a-π/4)=1/2 （1）求tana的直 （2）求sin2a-cosa的平方的直

（1）tan(a-π/4)= （tana-1)/(1+tana) =1/2 ,所以 tana=3；
（2）你第二个是sin2a-(cosa)^2还是sin2a-cos^2a呢

1、tan(a-π/4)=1/2
(tana-tan45°)/(1+tanatan45²)=1/2
(tana-1)/(tana+1)=1/2
2tana-2=tana+1
tana=3
2、(sin2α-cos²α)/(1+cos2α)
=(2sinαcosα-cos²α)/(1+2cos²α-1)
=(2sinαcosα-cos²α)/(2cos²α)
=(2sinα-cosα)/(2cosα)
=(2tanα-1)/2
=(6-1)/2
=5/2

(1)tan(a-π/4)=1/2（tana-tanπ/4）/（1+tanatanπ/4）=1/2（tana-1）/（1+tana）=1/22tana-2=1+tanatana=3(2)sin2a-cos²a=(2sinacosa-cos²a)/(sin²a+cos²a)=(2tana-1)/(tan²a+1)=(2×3-1...

(1)
tan(a-π/4)=1/2
(tana-tanπ/4)/(1+tanatanπ/4)=1/2
2(tana-1)=1+tana
tana=3
(2)
sin2a-cosa的平方
=2tana/(1+tan²a)-(1+cos2a)/2
=6/10-(1+(1-tan²a)/(1+tan²a))/2
=3/5-(1+(-8)/10)/2
=3/5-1/10
=1/2