Triangles

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Triangles

by masuarezdl » Wed Jul 15, 2009 11:06 am
In isoceles triangle RST what is the measure of angle R?

(1) The measure of angle T is 100deg.
(2) The measure of angle S is 40 deg.

Whats the logic behind this? I though both worked out alone sufficiently...

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Re: Triangles

by Morgoth » Wed Jul 15, 2009 11:14 am
masuarezdl wrote:In isoceles triangle RST what is the measure of angle R?

(1) The measure of angle T is 100deg.
(2) The measure of angle S is 40 deg.

Whats the logic behind this? I though both worked out alone sufficiently...
Statement I

if angle T is 100 the other 2 angles are equal since the triangle is an isosceles triangle. Also angle T cannot be equal to another angle because then the sum of the 2 angles will be greater than 180

T + R+S = 180
100+2R = 180 [since R=S]
R = 40

Sufficient.

Statement II
Angle S = 40

angle S could be equal to angle T or angle R we don't know which of the 2 angles are equal.

Insufficient.

Hence A.
Hope this helps.

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Re: Triangles

by masuarezdl » Wed Jul 15, 2009 11:42 am
Morgoth wrote:
masuarezdl wrote:In isoceles triangle RST what is the measure of angle R?

(1) The measure of angle T is 100deg.
(2) The measure of angle S is 40 deg.

Whats the logic behind this? I though both worked out alone sufficiently...
Statement I

if angle T is 100 the other 2 angles are equal since the triangle is an isosceles triangle. Also angle T cannot be equal to another angle because then the sum of the 2 angles will be greater than 180

T + R+S = 180
100+2R = 180 [since R=S]
R = 40

Sufficient.

Statement II
Angle S = 40

angle S could be equal to angle T or angle R we don't know which of the 2 angles are equal.

Insufficient.

Hence A.
Hope this helps.
I cannot believe i missed that... thanks!