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The vertices of a triangle are the points `P(-26, 17), Q(30, 17) and R(10, 2)`. If G and I be the centroid and incentre of the triangle PQR, then the value of `(GI)^(2)` is equal to

A

`(205)/(9)`

B

`(sqrt(205))/(3)`

C

`3sqrt3`

D

27

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the square of the distance between the centroid (G) and the incenter (I) of triangle PQR, where the vertices are given as P(-26, 17), Q(30, 17), and R(10, 2). ### Step 1: Find the Centroid (G) of Triangle PQR The formula for the centroid \( G \) of a triangle with vertices \( (x_1, y_1), (x_2, y_2), (x_3, y_3) \) is given by: \[ G = \left( \frac{x_1 + x_2 + x_3}{3}, \frac{y_1 + y_2 + y_3}{3} \right) \] Substituting the coordinates of points P, Q, and R: - \( P(-26, 17) \) - \( Q(30, 17) \) - \( R(10, 2) \) Calculating \( G \): \[ G_x = \frac{-26 + 30 + 10}{3} = \frac{14}{3} \] \[ G_y = \frac{17 + 17 + 2}{3} = \frac{36}{3} = 12 \] Thus, the centroid \( G \) is: \[ G = \left( \frac{14}{3}, 12 \right) \] ### Step 2: Find the Incenter (I) of Triangle PQR To find the incenter \( I \), we need the lengths of the sides of the triangle: - \( a = QR \) - \( b = PR \) - \( c = PQ \) Using the distance formula: \[ QR = \sqrt{(30 - 10)^2 + (17 - 2)^2} = \sqrt{20^2 + 15^2} = \sqrt{400 + 225} = \sqrt{625} = 25 \] \[ PR = \sqrt{(-26 - 10)^2 + (17 - 2)^2} = \sqrt{(-36)^2 + 15^2} = \sqrt{1296 + 225} = \sqrt{1521} = 39 \] \[ PQ = \sqrt{(-26 - 30)^2 + (17 - 17)^2} = \sqrt{(-56)^2 + 0^2} = \sqrt{3136} = 56 \] Now, we can find the incenter \( I \) using the formula: \[ I_x = \frac{a \cdot x_1 + b \cdot x_2 + c \cdot x_3}{a + b + c} \] \[ I_y = \frac{a \cdot y_1 + b \cdot y_2 + c \cdot y_3}{a + b + c} \] Substituting the values: \[ I_x = \frac{25 \cdot (-26) + 39 \cdot 30 + 56 \cdot 10}{25 + 39 + 56} \] Calculating the numerator: \[ = \frac{-650 + 1170 + 560}{120} = \frac{1080}{120} = 9 \] Now for \( I_y \): \[ I_y = \frac{25 \cdot 17 + 39 \cdot 17 + 56 \cdot 2}{25 + 39 + 56} \] Calculating the numerator: \[ = \frac{425 + 663 + 112}{120} = \frac{1200}{120} = 10 \] Thus, the incenter \( I \) is: \[ I = (9, 10) \] ### Step 3: Calculate \( GI^2 \) Now, we can calculate the square of the distance \( GI \): \[ GI^2 = (G_x - I_x)^2 + (G_y - I_y)^2 \] Substituting the values: \[ GI^2 = \left( \frac{14}{3} - 9 \right)^2 + (12 - 10)^2 \] Calculating \( G_x - I_x \): \[ = \frac{14}{3} - \frac{27}{3} = \frac{-13}{3} \] Calculating \( GI^2 \): \[ GI^2 = \left( \frac{-13}{3} \right)^2 + (2)^2 = \frac{169}{9} + 4 = \frac{169}{9} + \frac{36}{9} = \frac{205}{9} \] ### Final Answer Thus, the value of \( GI^2 \) is: \[ \boxed{\frac{205}{9}} \]
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