Question #5ec05 Geometry Angles and Intersecting Lines Angle Basics and Measurements 1 Answer A08 Jul 4, 2016 #10# sq. units. Explanation: Let #(x_1, y_1), (x_2, y_2) and (x_3, y_3)# be the co-ordinates of the vertices #A, B, C# respectively of the triangle #ABC#. Then area #Delta ABC = 1/2| x_1 (y_2 - y_3) + x_2 (y_3 – y_1) + x_3 (y_1 – y_2) | #sq. units. Given #(-2, 1), (1, 3) and (5, -1)# #:. Delta ABC =1/2| -2(3- (-1)) + 1 (-1 – 1) + 5 (1 – 3)|# #=> Delta ABC = 1/2| -2(4) + 1 (-2) + 5 (– 2)|# #=> Delta ABC = 1/2| -8 -2 – 10|# #=> Delta ABC = 10# sq. units. Answer link Related questions What is the diameter of a circle if its circumference is 25.8 inches? How do you find the measures of the angles of a triangle if the measure of one angle is twice... How can angles be adjacent? How are adjacent angles used in real life? How do you identify vertical angles? What are some examples of adjacent angles? How do you describe an acute angle? How do you bisect an acute angle? How do you find the related acute angle? How do you find the positive acute angle? See all questions in Angle Basics and Measurements Impact of this question 678 views around the world You can reuse this answer Creative Commons License