stupid math question
Discussion
well not so much a stupid question, more a stupid poster for not knowing the answer...
Two intersecting planes that are at 90 deg to each other along the base line, both leaning back at any given (but the same) angle. How do you calculate the angle of the intersection when viewing parallel to the plane of the slope?
Or another way of explaining it... you want to build a pyramid out of cardboard, and you want each side to slope back at say 25 degrees from vertical. You want to draw out each side on a piece of cardboard and cut it out. How do you calculate the angle of the sloping cuts.
Two intersecting planes that are at 90 deg to each other along the base line, both leaning back at any given (but the same) angle. How do you calculate the angle of the intersection when viewing parallel to the plane of the slope?
Or another way of explaining it... you want to build a pyramid out of cardboard, and you want each side to slope back at say 25 degrees from vertical. You want to draw out each side on a piece of cardboard and cut it out. How do you calculate the angle of the sloping cuts.
Cut the pyramid in half and you have a right angled triangle. You need to calculate the length of the long side (hypotenuse). Someone else will be along to tell you the rest 
I was never good at trigonometry so my cheat would be to draw it out in scale on paper and simply measure the length directly.
I was never good at trigonometry so my cheat would be to draw it out in scale on paper and simply measure the length directly.
Simpo Two said:
I was never good at trigonometry so my cheat would be to draw it out in scale on paper and simply measure the length directly.
Very difficult to draw out though, as if you draw from a single view point you are not taking into account that the hypotenuse is actually sloping back as well us up - so you can't measure from 2D.the internal angles of a triangle add up to 180 degrees, this may help.
please call it maths though
eta...
cut out the sides as rectangles with the desired width and length...then draw a line from the centre of one width to the
edges of the other end and cut, repeat for the four other sides...does that make sense?
please call it maths though
eta...
cut out the sides as rectangles with the desired width and length...then draw a line from the centre of one width to the
edges of the other end and cut, repeat for the four other sides...does that make sense?
Edited by CaptainSlow on Monday 20th October 20:30
Extend all the sides upwards until they meet at a point. You can calculate how high up they meet based on the angle of the sides and the width of the base. You can calculate the distance from the middle of the base of each side, to the point.
Each side is then an isosceles triangle, which you can cut in half to produce a right angle triangle. You know the width of the base of the triangle, you have calculated the length of the second side and from those you can calculate the angle you want.
If you want to know what angle you should chamfer the sides so they join up exactly, that's a much harder question.
Each side is then an isosceles triangle, which you can cut in half to produce a right angle triangle. You know the width of the base of the triangle, you have calculated the length of the second side and from those you can calculate the angle you want.
If you want to know what angle you should chamfer the sides so they join up exactly, that's a much harder question.
Davi said:
Two intersecting planes that are at 90 deg to each other
this will give an upward angle of approachDavi said:
build a pyramid out of cardboard... each side to slope back at say 25 degrees from vertical.
this will give a different angle (unless you happen to have hit the nail on the head at first guess!Davi said:
well not so much a stupid question, more a stupid poster for not knowing the answer...
Two intersecting planes that are at 90 deg to each other along the base line, both leaning back at any given (but the same) angle. How do you calculate the angle of the intersection when viewing parallel to the plane of the slope?
Or another way of explaining it... you want to build a pyramid out of cardboard, and you want each side to slope back at say 25 degrees from vertical. You want to draw out each side on a piece of cardboard and cut it out. How do you calculate the angle of the sloping cuts.
If they are at right angles to each other then you just need to add the amount you want them to slope back.Two intersecting planes that are at 90 deg to each other along the base line, both leaning back at any given (but the same) angle. How do you calculate the angle of the intersection when viewing parallel to the plane of the slope?
Or another way of explaining it... you want to build a pyramid out of cardboard, and you want each side to slope back at say 25 degrees from vertical. You want to draw out each side on a piece of cardboard and cut it out. How do you calculate the angle of the sloping cuts.
ie if you said you wanted them to slope back 25 degrees then just add 25 degrees to each pyramid half.
ie instead of being 90 degrees they would be 115 degrees.
GreenV8S said:
Extend all the sides upwards until they meet at a point. You can calculate how high up they meet based on the angle of the sides and the width of the base. You can calculate the distance from the middle of the base of each side, to the point.
Each side is then an isosceles triangle, which you can cut in half to produce a right angle triangle. You know the width of the base of the triangle, you have calculated the length of the second side and from those you can calculate the angle you want.
If you want to know what angle you should chamfer the sides so they join up exactly, that's a much harder question.
Each side is then an isosceles triangle, which you can cut in half to produce a right angle triangle. You know the width of the base of the triangle, you have calculated the length of the second side and from those you can calculate the angle you want.
If you want to know what angle you should chamfer the sides so they join up exactly, that's a much harder question.
that does the job cheers, didn't think of working out the length from the tip of a corner to the centre of the base which was the "missing" variable. Now if there is a formula to cut out some of the faffing...Gassing Station | The Pie & Piston Archive | Top of Page | What's New | My Stuff