Q. In △PQR,PR is extended through point R to point S,m∠PQR=(x+12)∘, m∠RPQ=(2x+7)∘, and m∠QRS=(7x−17)∘. Find m∠PQR.Answer:
Understand angles relationship: Understand the relationship between the angles in the problem.In any triangle, the sum of the interior angles is always 180 degrees. Additionally, the exterior angle of a triangle is equal to the sum of the two non-adjacent interior angles.
Set up equation: Set up the equation using the exterior angle theorem.The measure of angle QRS (exterior angle) is equal to the sum of the measures of angles PQR and RPQ.So, we have the equation: m∠QRS=m∠PQR+m∠RPQSubstitute the given expressions: (7x−17)∘=(x+12)∘+(2x+7)∘
Combine terms and solve: Combine like terms and solve for x. (7x−17)=(x+12)+(2x+7) 7x−17=3x+19 7x−3x=19+17 4x=36 x=9
Substitute value for measure: Substitute the value of x back into the expression for m∠PQR to find its measure.m∠PQR=(x+12)∘m∠PQR=(9+12)∘m∠PQR=21∘
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