你好
令x=sint,则t=arcsinx,dx=costdt,当x=0时,t=0,x=-1时,t=-π/2,
∫(-1,0)√(1-x∧2)dx
=∫(-π/2,0)costcostdt
=∫(-π/2,0)cos²tdt
=∫(-π/2,0)(1+cos2t)/2dt
=1/2t+sin2t/4│(-π/2,0)
=π/4
你好
令x=sint,则t=arcsinx,dx=costdt,当x=0时,t=0,x=-1时,t=-π/2,
∫(-1,0)√(1-x∧2)dx
=∫(-π/2,0)costcostdt
=∫(-π/2,0)cos²tdt
=∫(-π/2,0)(1+cos2t)/2dt
=1/2t+sin2t/4│(-π/2,0)
=π/4