正弦

正弦	zhèng xián	(math.) sine
正	zhēng	first month of the lunar year
正	zhèng	straight / upright / proper / main / principal / to correct / to rectify / exactly / just (at that time) / right (in that place) / (math.) positive
弦	xián	bow string / string of musical instrument / watchspring / chord (segment of curve) / hypotenuse / CL:根