Let’s say I have a curvy curve on the XY plane and I want to find the point where the tangent line is 30 degrees with the X-axis? How would you do this using just Rhino commands?

# How to find tangent point at 30 degrees?

**pascal**(Pascal Golay) #2

Hi Menno - a clunky way would be to make a 30 degree line nearby and use `ClosestPoint> Object`

to find the tangent point on the curve.

Or, rotate the CPlane 30 degrees and use the Quad OSnap to locate the point.

`! CPlane Rotate Z 30 Point Quad Pause CPlane Previous`

-Pascal

**jeff_hammond**#3

another–

make a line at 30º then use `_Move`

with Tangent oSnap.

select an endpoint of the 30º line then move it along the curvy curve… it will snap into place when tangent.

(i personally also use the **Near** osnap… that way, your moving curve is tracking along the curvy curve then clicks into place when tangent… not necessary but just behaves better (to me) )

**davidcockey**(David Cockey) #4

@pascal methods have a difference which may make one preferable.

[quote=“pascal, post:2, topic:45152”]

a clunky way would be to make a 30 degree line nearby and use ClosestPoint> Object to find the tangent point on the curve.

[/quote]This locates the single closest point on the curve to the line segment, which may be a tangent point or may be a kink, or depending on the length and position of the line segment the closest point to one end of the line segment which may not be a tangent point.[quote=“pascal, post:2, topic:45152”]

rotate the CPlane 30 degrees and use the Quad OSnap to locate the point.

! CPlane Rotate Z 30 Point Quad Pause CPlane Previous

[/quote]Only tangent points will be located with the Quad OSnap, and it will also locate all tangent points.

**davidcockey**(David Cockey) #5

This method also will only find tangent points, and can locate all tangent points.