If you select the dimensions you can RMB and Link Values so that they are equal. Or use equations to define them equal to a variable.
You could also do it with construction lines. In the screenshot the two construction lines that are closest to vertical are equal, and the other two are equal, with their endpoints coincident with the midpoints of the ones going across. As you can see the construction lines aren't fully defined yet, but they have the angles fully defined as equal after dimensioning one of them.