FACTORS AND TABLES OF EQUIVALENTS USED IN FoRESTRY 15 
TasLe 25.—Quarter girth;! equivalents in true girth, diameter, area, and volume, 
United States measurement and metric system 
Quarter girth unit United States measurement Metric system 
iach a true girth=4 inches____-________-________- In true girth=10.16 cm. 
TAG Ro haat ana er eg In diameter=1.2732 inches__-__.-------------- In diane tet eat cm. 
au j =0.118288 m2? per acre. 
1 square foot per acre________ = 1.2732 square feet per acre_---_-----------_- ae m? per hectare. 
l=noeres m3 per acre. 
1 cubic foot per acre____--__- =1.2732 cubic feet per acre__.______-_-_____- = 0.089092 m3 per hectare. 
1A British unit used customarily in East Indian forestry, equivalent to about 114 diameters. The 
converting factor from diameter to quarter girth would be a or 0.7854. 
TaBLE 26.—WNatural trigonometric functions, by half degrees 
Degree| Sin Cos Tan Degree Sin Cos Tan Degree Sin Cos Tan 
° 4 ie} , ° 7 
0 30 } 0.0087 | 1.0000 0. 0087 15 30 | 0. 2672 | 0. 9636 0. 2773 30 30 | 0.5075 | 0.8616 0. 5890 
1 . 0175 . 9998 .0175 16 . 2756 - 9613 . 2867 31 . 5150 . 8572 . 6009 
1 30 . 0262 . 9997 . 0262 16 30 . 2840 . 9588 . 2962 31, 30 . 5225 . 8526 . 6128 
2 . 0349 - 9994 . 0349 17 . 2924 . 9563 . 3057 32 . 5299 . 8480 . 6249 
2 30 . 0436 . 9990 . 0437 17 30 - 3007 - 9537 - 3153 32 30 . 5373 . 8434 . 63871 
3 . 0523 . 9986 . 0524 18 . 3090 . 9511 . 3249 33 . 5446 . 8387 . 6494 
3 30 . 0610 . 9981 . 0612 18 30 . 3173 . 9483 . 3346 33 30 . 6519 . 8339 . 6619 
4 . 0698 . 9976 . 0699 19 . 0206 . 9455 . 3443 34 . 5592 . 8290 . 6745 
4 30 . 0785 - 9969 . 0787 19 30 . 3338 . 9426 . 3041 34 30 . 5664 . 8241 . 6873 
5 . 0872 . 9962 . 0875 20 . 8420 . 9397 . 3640 35 . 5736 . 8192 . 7002 
5 30 . 0958 . 9954 . 0963 20 30 . 3502 . 9367 . 3739 35 30 . 5807 8141 . 7133 
6 . 1045 . 9945 . 1051 21 . 3584 - 9336 . 3839 36 . 5878 . 8090 . 7265 
6 30 . 1132 . 9936 . 1139 21 30 . 3665 . 93804 - 3939 36 30 . 5948 . 8039 . 7400 
7 . 1219 . 9925 . 1228 22, . 3746 . 9272 - 4040 37 . 6018 . 7986 . 7536 
7 30 . 1305 . 9914 . 1317 22 30 . 3827 . 9239 - 4142 37 «330 . 6088 . 79384 . 7673 
8 . 1392 . 9903 - 1405 23 . 3907 - 9205 . 4245 38 . 6157 . 7880 . 7813 
8 30 . 1478 . 9890 . 1495 23 30 . 3987 9171 . 4348 38 30 . 6225 . 7826 . 7954 
9 . 1564 . 9877 . 1584 24 . 4067 . 9135 . 4452 39 . 6293 T7771 . 8098 
9 30 . 1650 . 9863 . 1673 24 30 4147 . 9100 - 4557 39 30 . 6361 . 7716 - 8243 
10 . 1736 - 9848 . 1763 25 . 4226 . 9063 . 4663 40 . 6428 . 7660 . 8391 
10 30 . 1822 . 9833 . 1853 25 30 . 4305 . 9026 - 4770 40 30 . 6494 . 7604 . 8541 
11 . 1908 . 9816 . 1944 26 . 4384 . 8988 . 4877 41 . 6561 . 7547 . 8693 
11 30 . 1994 - 9799 . 2035 26 30 . 4462 . 8949 - 4986 41 30 . 6626 . 7490 . 8847 
12 . 2079 . 9781 . 2126 Pai . 4540 . 8910 . 5095 42 . 6691 . 7431 . 9004 
12 30 . 2164 . 9763 . 2217 27 ~=©30 4617 . 8870 . 5206 42 30 . 6756 . 7373 . 9163 
13 . 2250 . 9744 . 2309 28 . 4695 . 8829 . 5317 43 . 6820 . 7314 . 9325 
13 30 . 2334 . 9724 . 2401 28 30 4772 . 8788 . 5430 43 30 . 6884 . 7254 . 9490 
14 . 2419 . 9703 . 2493 29 - 4848 . 8746 . 5543 44 . 6947 . 7193 - 9657 
14 30} .2504] .9681 . 2586 29 30] .4924) .8704 . 5658 44 30] .7009 | .7133 . 9827 
15 . 2588 | . 9659 . 2679 30 . 5000 | . 8660 . 5774 45 7071 | .7071 | 1.0000 
