Video instructions and help with filling out and completing Are Form 2220 Consecutive

Instructions and Help about Are Form 2220 Consecutive

Hi welcome to math antics we're continuing our series on geometry and today we're going to learn about angles or in our last video we learned about points and lines and that's good because we're going to need lines to make angles so let's start with a couple of lines that are in the same plane we're only going to be dealing with two-dimensional geometry in this video these lines are conveniently called line a B and line C D now the important thing to notice about these two lines is that they're pointing in exactly the same direction so even if we extend them forever they would never cross or even get closer together when two lines are arranged like this we call them parallel now you've probably heard the term parallel before like parallel parking or a parallel universe or parallel bars okay so parallel lines are lines that will never cross even if they go on forever but what if I take one of our lines and give it a little nudge now the lines aren't parallel anymore in fact they cross at this point right here let's name it point P when lines cross at a point like this we say that they intersect and we call the point an intersection and when lines intersect they form angles you can think of the angles as the spaces or shapes that are formed between the intersecting lines these intersecting lines form four angles one two three four but instead of calling them angle one two three and four in geometry we name them by the points used to make them for example this angle here can be called angle D PB because if you trace along those points like connect the dots they outline that angle and this angle here we can call that angle APD because connecting those dots forms that angle now when naming angles there's a nice shorthand that we can use instead of writing the word angle over and over again we can just use the angle symbol instead which looks like this but there's an even simpler way to name angles to learn that way let's erase all the points and letters on our lines except for the intersection point and this one point here now imagine that the line segment between these two points can rotate around the point of intersection just like a clock hand rotates around the center of a clock let's also imagine that as we rotate the line segment the point out at the end leaves a trail like if a pencil was attached to it the trail or path that's left when we rotate the line segment all the way around forms a circle but if we only go part way around then it forms part of a circle that we call an arc this arc can represent the angle that's formed when we rotate the segment from one position to another like from this line to that one and now if we shrink down that arc so that it's close to the intersection point and then put a letter by it like the letter A we have another way of showing an angle angle a and we can do this with any angle so the angle up here we can also draw an arc and call it angle B so whenever you see a letter next to a little mark like this it means that it's the name of the angle formed by that arc alright then so now we have a diagram that shows angle a and angle B and you might notice that those angles aren't the same size B seems to be bigger than a but what if we rotate one of our lines until the angles do look like they're the same size now our angles look kind of like a plus sign lions arranged like this are called perpendicular perpendicular lines are lines that form square corners when they intersect and these square corner angles have a special name in geometry because they're really important we call them right angles there's even a special symbol that we use to show when an angle is a right angle because they form square corners we use a little square instead of the arc that we use for the other angles so whenever you see this symbol you know that the angle you're looking at is a right angle and that the lines that form it are perpendicular okay now that you know what a right angle is let's look at a simple one that's made from just two rays what will happen if we take the rate pointing up and rotate it like the hand of a clock a little bit to the right a little bit clockwise well we don't have a right angle anymore because the Rays are no longer perpendicular instead we have an angle that smaller or less than a right angle angles that are less than right angles are called acute angles on the other hand if we rotated our ray to the left instead of the right we would get an angle that's bigger or greater than a right angle angles that are greater than right angles are called obtuse angles so there are three main kinds of angles that you need to know about right angles acute angles and obtuse angles well actually there's one more type of angle that's pretty important but it's kind of a strange one it's called a straight angle a straight angle is just what we get when we rotate our rays so that they point in exactly opposite directions the result looks just like a straight line which is why it's called a straight angle all right then there's just a few more important geometry terms that we need to learn in this video let's look at our simple right angle again that's made from two rays but