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From this it is manifest, that if one angle of a triangle be equal to the other two, it is a right angle, because the angle adjacent to it is equal to the same two ; and when the adjacent angles are equal, they ate right angles.
Elements of Arithmetic, Algebra, and Geometry - Page 148
by George Lees - 1826

## The Elements of Euclid: The Errors, by which Theon, Or Others, Have Long Ago ...

Robert Simson - Trigonometry - 1762 - 488 pages
...fegment is faid to be lefs thai} ' a right angle.' COR. From this it is manifeft, that if one angle pf a triangle be equal to the other two, it is a right angle, becaufe the angle adjacent to it is equal to the fame two ; and when the adjacent angles arc equal,...

## A Royal Road to Geometry: Or, an Easy and Familiar Introduction to the ...

Thomas Malton - 1774 - 484 pages
...conf.theAng.A + ABC + BCA(eq.FBA+ABC+CBG) are equal to two Right Angles. - - - C. 3. Th. i. CnR. i. Hence, if one Angle of a Triangle be equal to the other two Angles, it is a Right one. For, if either Side, containing the Right Angle, be produced \ the external...

## The Elements of Euclid, Viz: The Errors, by which Theon, Or Others, Have ...

Robert Simson - Trigonometry - 1775 - 534 pages
...angle of the left « fegment is faid to be lefs, than a right angle.' CoR. From this it is manifeft, that if one angle of a triangle be equal to the other two, it is a right angle, becaufe the angle adjacent to it is equal to the fame two ; and when the adjacent angles are equal,...

## The Elements of Euclid: In which the Propositions are Demonstrated in a New ...

Euclid - Geometry - 1776 - 326 pages
...in an lequilateral triangle is one third of two right angles, or two thirds of one right angle. 6. If one angle of a triangle be equal to the other two, that angle is a right one ; for, if the fide is produced, the adjacent angle is equal to the other...

## The Elements of Euclid,: In which the Propositions are Demonstrated in a New ...

Euclid - Geometry - 1776 - 318 pages
...in an ^equilateral triangle is one third of two right angles, or two thirds of one right angle. 6. If one angle of a triangle be equal to the other two, that angle is a right one ; for, if the fide is produced, the adjacent angle is equal to the other...

## The Elements of Euclid: With Dissertations Intended to Assist and Encourage ...

Euclid, James Williamson - Euclid's Elements - 1781 - 324 pages
...wherefore the angle BAC is a right angle. Which was to be demonftrated. Cor From this it is manifeft that if one angle of a triangle be equal to the other two it is a right angle : for this reafon becaufe the adjacent angle is equal to the fame two : but (by def. 10. i.) when the...

## The Elements of Euclid: The Errors, by which Theon, Or Others, Have Long Ago ...

Robert Simson - Trigonometry - 1781 - 534 pages
...angle of the lefs feg~ient is faid to be lefs .' than a right angle.' CoR. From this it is Tnanifcit, that if one angle of a triangle be equal to the other two, it is a right angle, becaufe the angle Adjacent to it is equal to the fame two ; and when the adjacent angles are equal,...

## The First Six Books: Together with the Eleventh and Twelfth

Euclid - 1781 - 552 pages
...angle of thelcfa ' fegment is faid to be lefs, than a right angle.' CoR. From this it is manifeft, that if one angle of a triangle be equal to the other two, it is a right angle, becaufe the angle adjacent to it is equal to the fame two ; and when the ad jacent angles are equal,...