RWU
Technically you are correct. In practise, however, most pilots use he following rule, which avoids having to get out a calculator whilst wrestling with an aircraft down final approach:
Rule:
Crosswind component = windspeed x (degrees off runway heading/60)
This roughly mirrors the sine function; ie 30 kts @ 30deg off rwy heading = 30 x (30/60) = 15 kts across; or 30 @ 50deg off = 30 x (50/60) = 25 across.
When you are fighting the elements down the approach, you really don't have time to do other than 'ballpark' sums in your head, it's not a simulator up there.