hyperbolical-secant solution
双曲线正割解法

• installation diagram
• installation microscope
• instant
• instantaneity
• instantaneous amplitude
• instantaneous exposure
• instantaneous image
• instantaneous position
• instantaneous power
• instantaneous value
• instanteanous error measurement
• instant photography
• instant reset
• instat return mirror mechanism
• in-step condition
• instoscope
• Instrction
• instruction
• instruction code
• instruction register
• instructon set
• instrument
• instrumental error
• instrumental optics
• instrument analysis