The area formula for parallelograms (or parallelagrams if you misspell it) -- A = bh -- is pretty easy. But this video also covers the most common tricks your teacher can throw at you, like making you use SohCahToa and special triangles to solve for area. Also explained are how to make rectangles out of parallelograms, which sounds silly but is kind of the basis of most area formulas.
Areas of Trapezoids
This video covers basic trapezoids, of course, but more importantly it covers the problems that aren't quite so plug-and-chug. Isosceles trapezoids, for example, are trick questions used by most teachers because they force you to be able to split the trapezoid into right triangles that require SohCahToa or special triangles to find the height. Another common trick: funky trapezoids turned up on their end so that they don't even look like trapezoids.
Areas of Parallelograms & Trapezoids on X-Y Coordinate Axes
This is one of those trick questions that every teacher uses: they think that if they draw a figure on a grid instead of labeling the sides, their students will become confused by all the square roots of the distance formula. And they are right. But you should actually look forward to these problems, because if you do them right, 99% of the time you won't even need the distance formula!
Areas of Parallelograms & Trapezoids with SohCahToa
When you're supposed to find the area of a parallelogram or trapezoid and they give you an angle as well as a side, chances are you're supposed to use SohCahToa (trig). Sometimes you have to use special triangles even if no angles are given, because you're "supposed to know" the special triangle ratios! Wow. This video shows you what to look for.
Parallelagram & Trapezoid Area Word Problems
Yeah, word problems! What happens to the area of a rectangle when you "tip it over" into a parallelogram? How can one use triangles to approximate the area of a trapezoidal airplane wing? What to do when you are given the area of a trapezoid and have to then solve for x? Why am I asking all these rhetorical questions?
If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)