https://www.explainxkcd.com/wiki/api.php?action=feedcontributions&feedformat=atom&user=172.68.24.165explain xkcd - User contributions [en]2026-06-24T14:54:21ZUser contributionsMediaWiki 1.30.0https://www.explainxkcd.com/wiki/index.php?title=Talk:2509:_Useful_Geometry_Formulas&diff=217331Talk:2509: Useful Geometry Formulas2021-08-31T04:46:40Z<p>172.68.24.165: </p>
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Area formulas are for 2D object as seen instead of surface of a projected 3D object. Sebastian --[[Special:Contributions/162.158.89.200|162.158.89.200]] 02:36, 31 August 2021 (UTC)<br />
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The "decorative stripes and dotted lines" are the parts of the diagrams that are intended to indicate the third dimension. The conceit of the comic is that these are superfluous. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 02:56, 31 August 2021 (UTC)<br />
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Ca someone explain how the last one works? [[User:GcGYSF(asterisk)P(vertical line)e|GcGYSF(asterisk)P(vertical line)e]] ([[User talk:GcGYSF(asterisk)P(vertical line)e|talk]]) 04:28, 31 August 2021 (UTC)<br />
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''bh'' is the area of the front face. The top face is a parallelogram with sides ''d'' and ''b'', with an angle of ''θ'' between them, so its area is ''d b sin(θ)''. The right face is a parallelogram with sides ''d'' and ''h'', with an angle of ''90º - θ'' between them, so its area is ''h d sin(90º - θ) = h d cos(θ)''. So the area of the whole picture is ''bh + d b sin(θ) + d h cos(θ)''.<br />
--[[Special:Contributions/172.68.24.165|172.68.24.165]] 04:46, 31 August 2021 (UTC)</div>172.68.24.165