"As a mathematical term khordē (and chord) means a line connecting two points on an arc A and B; if we draw lines from A and B to the centre of the circle (O) the length of the chord AB is defined as the chord of the angle AOB. The Indians borrowed Greek trigonometry and translated khordē literally as jyā, but they used this word not (usually) for a chord but for a half-chord, what we call a sine.
The Arabic astronomers inherited both the Greek and the Indian systems of trigonometry and the Sanstrit word jyā (jīva) was transcribed (not translated) as jīb. In the 12th century the famous Arabic-Latin translator Gerard of Cremona misread the latter as jayb “breast pocket” and rendered this with its Latin equivalent sinus.
Sin²φ is odious to me, even though Laplace made use of it; should it be feared that sin²φ might become ambiguous, which would perhaps never occur, or at most very rarely when speaking of sin(φ²), well then, let us write (sin φ)² not sin²φ, which by analogy should signify sin(sin φ)
"As a mathematical term khordē (and chord) means a line connecting two points on an arc A and B; if we draw lines from A and B to the centre of the circle (O) the length of the chord AB is defined as the chord of the angle AOB. The Indians borrowed Greek trigonometry and translated khordē literally as jyā, but they used this word not (usually) for a chord but for a half-chord, what we call a sine.
The Arabic astronomers inherited both the Greek and the Indian systems of trigonometry and the Sanstrit word jyā (jīva) was transcribed (not translated) as jīb. In the 12th century the famous Arabic-Latin translator Gerard of Cremona misread the latter as jayb “breast pocket” and rendered this with its Latin equivalent sinus.
all notation is stupid…