Reply 1
First off, draw a picture.
Well, what do you know about right angles (i.e. two lines are perpendicular) in a coordinate system?
Well, what do you know about right angles (i.e. two lines are perpendicular) in a coordinate system?
Original post by tonyiptony
First off, draw a picture.
Well, what do you know about right angles (i.e. two lines are perpendicular) in a coordinate system?
Well, what do you know about right angles (i.e. two lines are perpendicular) in a coordinate system?
The first thing that comes to mind is that the gradient of one line is the reciprocal of the other.
Reply 3
Original post by Skybird
The first thing that comes to mind is that the gradient of one line is the reciprocal of the other.
Almost. You missed a minus sign (or really, I like to remember that multiplying two gradients will be -1). But anyhow, a good start.
You now know there is something to do with gradients of two lines (which two in this instance?), then surely it's not a bad idea to just calculate gradients.
As AC is opposite the right-angle we know it is the hypotenuse. If we calculate the gradients of AB and BC we know that the product of the gradients is -1. So after some cross-multiplying, you get to a quadratic which can be factorised giving two values for b: 1 and 6. The question asks for a value of b > 3, so the answer is 6.
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