How to find area of irregular 2D quadrilateral?

Question

find area of irregular 2D quadrilateral,

please answer showing work with:

side lengths 1, 2, 3, 4

side lengths a, b, c, d

where 1 is opposite 3, 2 opp 4, a opp c, b opp d

Note: this is to check my (already completed) work in chemistry, it is NOT a homework problem.

Answer 1

It's impossible to calculate the area from the lengths of four sides alone. You need to know the angles between the sides as well.

In general, the area of a quadrilateral can be found by:

Area = (ad sin A + bc sin B)/2

where:

A = angle between a and d

B= angle between b and c

Answer 2

You should divide the quad to see if you get any triangles. or squares or whatever for for which you know the area. Heck, I actually think there was some formula... oh well, that was 5 years ago, I don't know.