tito1545 wrote:Could someone give me a step by step approach for this please ?
In isosceles triangle RST what is the measure of angle R ?
(1) The measure of angle T is 100 degrees
(2) The measure of angle S is 40 degrees
In an isosceles triangles, 2 angles are equal. The sum of the all 3 angles in any triangle is 180.
Statement 1: The measure of angle T is 100 degrees.
100-100-x is impossible because 100+100 = 200, and the sum of all 3 angles is 180.
Thus, the 3 angles are 100-40-40, and angle R = 40.
Sufficient.
Statement 2: The measure of angle S is 40 degrees.
The 3 angles could be 40-40-100 or 40-70-70.
No way to determine whether R=40, R=70, or R=100.
Insufficient.
The correct answer is
A.
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