# Math

Given ABC with a = 23, b = 17, and c = 19, find mA . Round the cosine value to the nearest thousandth and answer to the nearest hundredth.

1. 👍 0
2. 👎 0
3. 👁 155
1. A simple application of the cosine law:
23^2 = 17^2 + 19^2 - 2(17)(19)cosA
solve for cosA, set your calculator to degrees, press 2nd F cos
(I anticipate an obtuse angle, since cosA will be negative.)

let me know what you get

1. 👍 1
2. 👎 0
2. I got 4

1. 👍 0
2. 👎 0
3. You are looking for the size of the angle.
You got 4 ?????

from:
23^2 = 17^2 + 19^2 - 2(17)(19)cosA
529 = 289+361 - 646cosA
646cosA = 121
cosA = 121/646
angle A = appr 79.20° to the nearest hundredth

I was wrong to guess that the cosine would turn out negative

1. 👍 1
2. 👎 0

## Similar Questions

1. ### Trig - Law of sines and cosines

ABC is an equilateral triangle with side length 4. M is the midpoint of BC, and AM is a diagonal of square ALMN. Find the area of the region common to both ABC and ALMN. I drew the diagram but I don't know how to find the answer?

asked by Sam on November 19, 2013
2. ### maths-urgently needed

In right angled triangle ABC angle B=90 degree and AB= root 34 unit. The coordinates of point B and Care (4,2)and (-1,y) respectively. If area of triangle ABC = 17 sq.units, then find value of y.

asked by Anonymous on February 12, 2013
3. ### geometry

1. Triangle ABC has a 63.0-degree angle at B, and side AC is 13.6 cm long. What is the diameter of the circle circumscribed about ABC? 2. And: Given any triangle ABC, with sides a, b, and c opposite angles A, B, and C,

asked by Esi on April 12, 2010
4. ### Math

BM and CN ARE ALTITUDES OF TRIANGLE ABC.IF AB=3.5cm,AC=3.2cm,AND BM=2.1cm ,calculate the area of triangle ABC and hence find CN

asked by Anonymous on January 6, 2020
5. ### Orthocenter Question

Triangle ABC has vertices A(0,6), B(4,6) and C(1,3) Find the orthocenter of triangle ABC. Please show your work so that I can understand how to do this type of problem. Thank You I really appreciate your help ^_^

asked by Hilary on January 3, 2012
1. ### Geometry

using a ruler and a pair of compasses only. construct triangle.ABC in which angle BAC=45 °.Then |AB|=7cm.then |AC|=9cm.locate P into triangle ABC which is 5cm from A and B equidistant from B and C. find PB.

asked by latif on January 19, 2020
2. ### Geometry

1. If RST=NPQ, which of the following is true? A) R=P B) R=Q C) T=P D) T=Q

asked by anonymous on December 20, 2017
3. ### geometry

Algebra BD bisects

asked by Jane on September 14, 2012
4. ### Math

Write a sequence of transformations that maps triangle ABC onto triangle A''B''C''. --------------------------------------… A in ABC is 1,9, B in ABC is 3,12, and C in ABC is 4,4. A'' in A''B''C'' is 3,-3, B'' in A''B''C'' is

asked by Cali on January 26, 2017
5. ### trigonometry

1. What is the area of triangle ABC if a = 47.0°, β = 57.8°, and a = 10.2 cm? A. 58.2 cm2 B. 43.5 cm2 C. 38.4 cm2 D. 33.3 cm2 2. Given triangle ABC with β = 41°, g = 14°, and a = 5.0, find the value of c. A. 6.2 B. 4.0 C.

asked by Erick on November 28, 2012
6. ### Math

ABC has vertices A(0, 6), B(4, 6), and C(1, 3). Find the orthocenter of ABC?

asked by bob on November 11, 2017