t一二图 √4+4tan²t=2|sect|=2/|cost|
将t∈[0,π/2]
√4+4tan²t=2|sect|=2/|cost|=2/cost
tan²t+1=sec²t=1/cos²t
(tan²t+1)^(3/2)=(sec²t)^(3/2)=(1/cos²t)^(3/2)=1/(cost)^3
∫sin3x dx=(1/3)∫sin3x d(3x)=(-1/3)cos3x
[(-1/3)cos3x]'=sin3x
t一二图 √4+4tan²t=2|sect|=2/|cost|
将t∈[0,π/2]
√4+4tan²t=2|sect|=2/|cost|=2/cost
tan²t+1=sec²t=1/cos²t
(tan²t+1)^(3/2)=(sec²t)^(3/2)=(1/cos²t)^(3/2)=1/(cost)^3
∫sin3x dx=(1/3)∫sin3x d(3x)=(-1/3)cos3x
[(-1/3)cos3x]'=sin3x