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Sines and Cosines. Question. Please Help?



Still helping the children. Last few questions THEY say... Thankyou so much for helping me out with these questions! Please put down any formula's or any work so that I may try to understand! Thankyou! The points will go to the best explained answer! Good day!

A hiking trail is marked out. The map,maker wants to supply bearings for the leaflet that describe the trail. Calculate the measures of the angles between the paths. Round your answers to the nearest tenth for each trail.

Image:

http://i184.photobucket.com/albums/x13/m...

Hi,

Use the Law of Cosines:

b虏 = a虏 + c虏 -2ac cos B
17.4虏 = 9.8虏 + 11.2虏 -2(9.8)(11.2) cos B
302.76 = 96.04 + 125.44 - 219.52 cos B
81.28 = -219.52 cos B
81.28/(- 219.52) = cos B
-.3703 = cos B
B = cos^(-1) (.3703) = 111.7掳

a虏 = b虏 + c虏 -2bc cos A
9.8虏 = 17.4虏 + 11.2虏 -2(17.4)(11.2) cos A
96.04 = 302.76 + 125.44 - 389.76 cos A
-332.16 = -389.76 cos A
-332.16/(- 389.76) = cos A
.8522 = cos A
A = cos^(-1) (.8522) = 31.5掳

C = 180 - A - B = 180 - 31.5 - 111.7 = 36.8掳

I hope that helps!! :-)
cos B= (a虏 + c虏 - b虏)/ 2ac ...Use when given 3 sides

cos B= (9.8虏 + 11.2虏 - 17.4虏)/ 2(9.8)(11.2)
B= cos^-1[ (9.8虏 + 11.2虏 - 17.4虏)/ 2(9.8)(11.2) ]
B = cos^(-1) (.3703)
B = 111.7掳

similarily for other angles

cos A= (b虏 + c虏 - a虏)/ 2bc
use COS rule
a(a)=b(b)+c(c)- 2bc cosA
b(b)=a(a)+c(c)- 2ac cosB
c(c)=a(a)+b(b)- 2bc cosC
a, b,c stand for length n A is angle
NOTE:a is opposite to A(in simple words, a is facing A), n so on for b&B and c&C.

im not sure which angle u want, so i wil calculate or

angle A
9.8(9.8)=17.4(17.4)+11.2(11.2) - 2 (17.4)(11.2) cos A
96.04=302.76+125.44 - 389.76 cos A
96.04-302.76-125.44=-389.76 cos A
-332.16=-389.76 cosA
389.76 cos A=332.16
cos A=332.16/389.76
A=31.5464 degree (to change get rid or cuz, use shift pewer negative 1 on 322.16/389.76)


angle B
17.4(17.4)=9.8(9.8)+11.2(11.2) - 2 (9.8)(11.2) cos B
302.76=96.04+125.44 - 219.52cos B
302.76-96.04-125.44=-219.52 cos B
81.28=-219.52 cos B
cos B=81.28/-219.52
B=111.7318degree

angle C
11.2(11.2)=9.8(9.8)+17.4(17.4) - 2 (9.8)(17.4) cos C
125.44=96.04+302.76 - 341.04cos C
125.44-96.04-302.76=-341.04cos C
-273.36=-341.04 cos C
cos C=-273.36/-341.04
C=36.7218degree


check
A+B+C=18O degree
34.2530 +111.7318+use COS rule
a(a)=b(b)+c(c)- 2bc cosA
b(b)=a(a)+c(c)- 2ac cosB
c(c)=a(a)+b(b)- 2bc cosC
a, b,c stand for length n A is angle
NOTE:a is opposite to A(in simple words, a is facing A), n so on for b&B and c&C.

im not sure which angle u want, so i wil calculate or

angle A
9.8(9.8)=17.4(17.4)+11.2(11.2) - 2 (17.4)(11.2) cos A
96.04=302.76+125.44 - 389.76 cos A
96.04-302.76-125.44=-389.76 cos A
-322.16=-389.76 cosA
389.76 cos A=322.16
cos A=322.16/389.76
A=34.2530 degree (to change get rid or cuz, use shift pewer negative 1 on 322.16/389.76)


angle B
17.4(17.4)=9.8(9.8)+11.2(11.2) - 2 (9.8)(11.2) cos B
302.76=96.04+125.44 - 219.52cos B
302.76-96.04-125.44=-219.52 cos B
81.28=-219.52 cos B
cos B=81.28/-219.52
B=111.7318degree

angle C
11.2(11.2)=9.8(9.8)+17.4(17.4) - 2 (9.8)(17.4) cos C
125.44=96.04+302.76 - 341.04cos C
125.44-96.04-302.76=-341.04cos C
-273.36=-341.04 cos C
cos C=-273.36/-341.04
C=36.7218degree


check
A+B+C=18O degree
31.5464 +111.7318+36.7218=180
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