U. S. GEOLOGICAL SURVEY 



PROFESSIONAL PAPER 129 PLATE VIH 



1,000- 



900- 



800- 



700- 



600- 



500- 



WO- 



300- 



200- 



100- 



b o 





^ 



o 



o 



Angle of slope (CTsca/e) 



o 

 r- 



J_ 



to 



J_ 



o 



^ 



-Or, 



'% 



'% 



\ k sca/e 



'% 



f^ 



10 



Index chart, c^^sine condition 





V. 



% 



A! 





'^O. 



'oy.. 







/Index chart, tan|ent condition 



% 





ndex chart, sine condition 



% 



<h 



^n 



% 



% 



O 



o 



-i-n- 



INSTRUCTIONS 



Sine condition. Connect value of angle of slope on the right- 

 hrnd scale with value of vertical distance by a straight line, 

 and this line will intersect the slope-distance scale, giving the 

 required value of slope distance. 



Cosine condition. Connect value of angle of slope on the upper 

 scale with value of horizontal distance by a straight line, and 

 this line will intersect the slope-distance scale, giving the 

 required value of slope distance. 



Tangent condition. Usea transparent index of two lines, drawn 

 at right angles. Pass one line through the given values of 

 horizontal and vertical distances and the other hne through 

 the lower left-hand corner of the chart. The continuation 

 of the second line will then intersect the diagonal line of 

 slope scale, giving the required value of angle of slope. 



Horizontal distance (h sca/e) 



^ 



-10'' 



5 



IT) 



0) 

 Q. 



_o 



(0 



o 



j; - 



c 



< 



-20° 



-30" 



o 

 o 



CM 



o 

 o 



T 

 o 



-n- 



-'rO" 



o 

 o 



o 



o 



ID 



o 

 o 



o 

 o 

 CO 



I I I 



-50" 



-60" 



-70" 



-80° 

 -90° 



o 



o 



CD 



O 

 O 



ALINEMENT CHART FOR THE GRAPHIC SOLUTION OF RIGHT TRIANGLES. 



