SAT Math : How to find out if lines are perpendicular

Study concepts, example questions & explanations for SAT Math

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Example Questions

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Example Question #88 : Coordinate Geometry

Which of the following lines is perpendicular to y=3x-4

Possible Answers:

y=\frac{1}{3}x+4

y=-\frac{1}{3}x-4

y=\frac{1}{3}x-4

y=-3x-4

Correct answer:

y=-\frac{1}{3}x-4

Explanation:

The line which is perpendicular has a slope which is the negative inverse of the slope of the original line. 

Example Question #191 : New Sat

Trans

Lines P and Q are parallel. Find the value of .

Possible Answers:

Correct answer:

Explanation:

Since these are complementary angles, we can set up the following equation.

 

Now we will use the quadratic formula to solve for .

Note, however, that the measure of an angle cannot be negative, so  is not a viable answer. The correct answer, then, is 

 

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