. Trigonometria. aSls the leg put for RadiusIs to Radius - \ So is the other leg To the tangent of his oppoftteangle. Prop ?. In every plain Triangle, the fides are propsrtional to thep fines of the oppofite angles. And the contrary. Let the triangle A BCbeinfcribed in a circle, and from thecenter D draw the Radii D F, D E, D G, bi-(e£ting as well theperipheries as their fubtenfes. And let there bs alfo drawn the Ra-dius D C, now becaufe the angle at the center E D C is equal tothe angle in the periphery A B C,and CDF equal to C A B, bythe 70 of the $. of Euclid, therefore (hall the halves of
. Trigonometria. aSls the leg put for RadiusIs to Radius - \ So is the other leg To the tangent of his oppoftteangle. Prop ?. In every plain Triangle, the fides are propsrtional to thep fines of the oppofite angles. And the contrary. Let the triangle A BCbeinfcribed in a circle, and from thecenter D draw the Radii D F, D E, D G, bi-(e£ting as well theperipheries as their fubtenfes. And let there bs alfo drawn the Ra-dius D C, now becaufe the angle at the center E D C is equal tothe angle in the periphery A B C,and CDF equal to C A B, bythe 70 of the $. of Euclid, therefore (hall the halves of the fidesbe as fines,and what proportion the fide CA hath to the fide CB,the fame (hall the fine C H have to the fine C I; for what pro-portion the whole hath to the whole, the fame (hall the half have to the half. Prop. 4. In every plain Triangle, As thefum of the two fides, is to their difference^ So isthe tangent of the halffitmme of the opyofite an-gles % to the tangent of half their difference, v In the Obl
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Keywords: ., bookcentury1600, bookdecade1650, bookidtrigonometri, bookyear1658
