Determine the nature of the triangle ABC, the measurements of his angles of which are respectively, a, b, c such as:

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- Dec 21st 2009, 10:12 AMdhiabNature of the triangle
Determine the nature of the triangle ABC, the measurements of his angles of which are respectively, a, b, c such as:

- Dec 22nd 2009, 01:54 AMGrandad
Hello dhiabIt is isosceles, with .

This may be proved by trigonometry formulae:

, since

, since and both lie between and

is the foot of the perpendicular from to . ThenGrandad

is the mid-point of

is isosceles with . - Dec 22nd 2009, 07:15 AMred_dog
Another approach: