Unequal Pitch Roof Trigonometry Calculating unequal pitched roofs is easy if you know what trigonometry functions to use. The formulas below use the law of sines to calculate the unknown length or angle. Known Variables: Major Pitch Angle & Minor Pitch Angle & Major Run Calculate Minor Run Minor Run = Major Run × ( tan(Major Pitch Angle) ÷ tan(Minor Pitch Angle)) Minor Run = Major Run × ( Major Pitch ÷ Minor Pitch) Known Variables: Major Pitch Angle & Minor Pitch Angle & Minor Run Calculate Major Run Major Run = Minor Run × ( tan(Minor Pitch Angle) ÷ tan(Major Pitch Angle)) Major Run = Minor Run × ( Minor Pitch ÷ Major Pitch) Known Variables: Major Pitch Angle & Minor Pitch Angle & Span Calculate Major & Minor Runs Major Run = ((Span × sin(Minor Pitch Angle)) ÷ sin (180  Major Pitch Angle  Minor Pitch Angle)) × cos( Major Pitch Angle ) Minor Run = ((Span * sin(Major Pitch Angle)) ÷ sin (180  Major Pitch Angle  Minor Pitch Angle)) × cos( Minor Pitch Angle ) Known Variables: Major Pitch Angle & Minor Pitch Angle & Span Calculate Major & Minor Rise Major Rise = ((Span × sin(Minor Pitch Angle)) ÷ sin (180  Major Pitch Angle  Minor Pitch Angle)) × sin( Major Pitch Angle ) Known Variables: Major Pitch Angle & Minor Pitch Angle & Span Calculate Major & Minor Rafter Lengths Major Rafter = (Span × sin(Minor Pitch Angle)) ÷ sin (180  Major Pitch Angle  Minor Pitch Angle) Minor Rafter = (Span * sin(Major Pitch Angle)) ÷ sin (180  Major Pitch Angle  Minor Pitch Angle) Known Variables: Major Pitch Angle & Major Run & Span Calculate Minor Pitch & Minor Run Minor Pitch Angle = arctan((Major Run × sin(Major Pitch Angle)) ÷ (Span  Major Run )) Minor Run = ((Span * sin(Major Pitch Angle)) ÷ sin (180  Major Pitch Angle  Minor Pitch Angle)) × cos( Minor Pitch Angle ) Known Variables: Minor Pitch Angle & Minor Run & Span Calculate Major Pitch & Major Run Major Pitch Angle = arctan((Minor Run × sin(Minor Pitch Angle)) ÷ (Span  Minor Run )) Major Run = ((Span × sin(Minor Pitch Angle)) ÷ sin (180  Major Pitch Angle  Minor Pitch Angle)) × cos( Major Pitch Angle ) Law Of Sines C = 180°  (A + B) a = ( c × sin( A) ) ÷ sin( C) a = ( b × sin( A ) ) ÷ sin( B) a = ( b ÷ sin( B ) ) × sin( A) b = ( c × sin( B ) ) ÷ sin( C) b = ( a × sin( B ) ) ÷ sin( A) b = ( a ÷ sin( A ) ) × sin( B) h = b × sin( A ) h = a × sin( B ) c = ( a × sin( C ) ) ÷ sin( A) c = ( b × sin( C ) ) ÷ sin( B)
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WindsorOne Protected Trim
 SBE Builders 5305 Laguna Ct. Discovery Bay, California 94505 (925) 6346022 • Fax: (925) 6346022
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