Given points A (2; -1), B (2; 3) and C (-1; -1) Find angle A.
| June 23, 2021 | education
Find the coordinates of vectors AB and AC:
AB = (2 – 2; 3 – (-1)) = (0; 4);
AC = (-1; -1 – (-1)) = (-3; 0).
The cosine of the angle between these vectors will be:
cos (A) = AC * AB / | AC | * | AB | = ((0 * (-3) + (4 * 0)) / 3 * 4 = 0
Then the angle A is equal to:
A = arccos (0) = 90.
Answer: 90 degrees.
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