Finding AREA for Triangles!
Finding the area of a triangle is easy to do once we learn what a triangle is! For this lesson, we will be using a special kind of triangle called a right triangle. Right triangles are triangles that have a 90 degree angle! Let's define what a triangle is, ready?
A triangle is a 2D shape with THREE sides and THREE angles. Triangles are closed shapes. We see many different types of triangles all the time, but for finding area we will be using the right triangle that we mentioned before! |
![Picture](/uploads/7/8/1/7/78175306/right-triangle1_1_orig.jpg)
Now that we know what a triangle is, we can look at our formula for finding the area of a triangle.
The formula looks like this:
A = 1/2 B x H (this means one HALF base times height)
Remember from our rectangle exploration that base and height can be different depending on which line we choose to make our base. The same rules apply for triangles!
Look to the right triangle to the side. I've made our BASE pink, just like before. Our HEIGHT is blue, just like before. If we add some numbers to this, we'll be able to find our area, won't we? Not quite yet!
The formula looks like this:
A = 1/2 B x H (this means one HALF base times height)
Remember from our rectangle exploration that base and height can be different depending on which line we choose to make our base. The same rules apply for triangles!
Look to the right triangle to the side. I've made our BASE pink, just like before. Our HEIGHT is blue, just like before. If we add some numbers to this, we'll be able to find our area, won't we? Not quite yet!
![Picture](/uploads/7/8/1/7/78175306/right-triangle2.png?250)
This time, our formula has a special part. Our formula includes the words "One half" (or 1/2). This means that we can't just multiply the base times the height like we did for a rectangle, but we can do this if we change our shape, like we did for parallelograms. Remember, whenever we can, we like to get back to our rectangle. Do you remember when we learned that squares can be rectangles too? Well, we can duplicate (or double!) our triangle, and do some flipping around to turn our right triangle into a square (or rectangle!) Then we can use the base x height formula we know.
See friends, the picture to the side is the same triangle! But now it looks like a rectangle. This doesn't mean we can use the formula base x height though. We now have TWO triangles, that's more space than just ONE triangle. This is why we use HALF the base and HALF the height, otherwise we'd be finding the area of a rectangle!
See friends, the picture to the side is the same triangle! But now it looks like a rectangle. This doesn't mean we can use the formula base x height though. We now have TWO triangles, that's more space than just ONE triangle. This is why we use HALF the base and HALF the height, otherwise we'd be finding the area of a rectangle!
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If you think you're ready to go through this formula again, and you want to try to work on a problem, go ahead and watch the video to the side! Remember to pause so that you have the chance to try the problem for yourself.
Did you get the same answer that I did? Can you tell me how you got that answer? Fantastic! Can you tell me what I'd be doing wrong if I just did base x height? |