Measuring the legs of the triangle instead of the hypotenuse in Fusion 360 sketch

When creating a sketch in Fusion 360, when drawing lines at an angle, it shows the length of the line:

• The hand-drawn portion of your sketch shows the height, not the base. You currently do not have a defined base in the drawing. If one presumes to create a right triangle from the apex of the 13.9 mm line, you can use a construction line, which will provide a dimension, but still not the base. It appears you currently have a line for the base but not of the proper length. – fred_dot_u Apr 12 '20 at 11:07
• @fred_dot_u: I don't follow to be honest. I want the green length to be 10mm. I guess I can do it with a construction line, but is it possible without? – pupeno Apr 12 '20 at 12:12
• Easy, place a point somewhere, press "d" for dimension and click point and than "your long base" and set it to 10; now draw a line between the point and the end point of the base. But, that is pretty useless, you also need to know the distance from the Y-axis. Why not sketch a rectangle of 10 high? Then you can draw the triangle in it. – 0scar Apr 12 '20 at 18:58
• So why do you want that value? It's easily calculated since you know the line length and the angle. You can calculate that value "offline" and then construct whatever other shape you want to add to the existing drawing. – Carl Witthoft Apr 14 '20 at 15:43
• @CarlWitthoft: I want to make the piece 5mm tall, with a 70 degree side of whatever length it is. So, calculating it is not what I'm after, but constraining it. – pupeno Apr 16 '20 at 7:32

2. press x to go into the construction-line mode
3. pres l for the line tool
6. press d to go into defining distance mode
9. press x again to get back to normal lines.