Let the intersection of dotted lines be o.

AO=4, which is the same as the height of triangle ABD given in the title, and the vertical BD of ao can be obtained.

Then from the triangle AOD, we can get AD=5,

CD is perpendicular to AD, and the area of triangle ACD is 10.

However, did you draw the following picture? If you do, what I want to say is that the connection between vernal equinox and A on BD may not be perpendicular to BD, which means what I did above is wrong. .

If the top view shows the length of two line segments on BD and is the same as the main view, you can draw a three-dimensional view like yours. And what I did above is ok. .