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Lines in Plan rectangular coordinate system, 屏幕快照 2021-01-12 上午8.51.21,…
Lines in Plan rectangular coordinate system
Parallel Lines
Example
Definition: Lines that always have distance between each other(The two lines both need to be strait lines, it can't be line segment or ray), in another word, two strait lines that never intersect are called parallel lines
How to determine they are parallel lines or not from the equation: if two lines have the same slope, they are then parallel. For example y=3x+1 and y=3x+9 are parallel lines because they have the same slope.
Perpendicular Lines
Definition: When two lines intercept and the intersection angle of them are right angles, in another word, 90 degrees angle, they are defined as perpendicular lines. Perpendicular lines have all four intersection angles the same angle, which is 90 degree
Example:
How to determine they are perpendicular lines from the equation: The slope of the two equations are negative reciprocals, which in another word, when they got multiplied, the answer will be -1.
Example 2: 114514x -1/114514=-1
Example 1: 1x-1=-1
Example 3: 3x-1/3=-1
Example 4: 7x-1/7=-1
Example 5: 5x-1/5=-1
Example of the 2 kinds of line
Perpendicular lines
Neither:
Parallel lines
The lines above are parallel lines
Negative reciprocals
Definition of reciprocals: If two number were multiplied and have the answer of 1, then the two numbers are called the reciprocals. For example the reciprocal of 5 is 1/5. One thing to mention is that one also have reciprocal, which is one. But 0 doesn't have one.
Definition of negative reciprocals: Negative reciprocals are similar to reciprocals. If two number were multiplied and get the answer of -1, then the two numbers are called a negative numbers. For example the negative reciprocals of 1 is -1.
