Math Is Fun Forum

Greaterpathmagician

Member

Registered: 2009-06-16

Posts: 32

Trigonometry

Q.1 Find the value of x in the diagrams below

shown in the uploaded image

I think you use the cosine rule:  Cos A=b^2+ C^2-a^2/2bc     

Q.2
A sailing course is typically set out in triangle formation. From a start point two markers (A and B) have been positioned to form a triangle for the sailing course. Marker A is on a bearing of 30º and is 2.5 km from the start. Marker B is an angle of 100º from the start and is positioned 3.2 km from the site.

a) Draw a diagram to represent the course
b)Find the total length of the course

I don’t know how to simply draw the diagram to represent the course but I am guessing that for b) you use the sine rule to a/sin⁡〖A 〗 =b/sin⁡B =c/(Sin C)

Thank you for any help

Last edited by Greaterpathmagician (2009-09-20 20:28:38)

juriguen

Member

Registered: 2009-07-05

Posts: 59

Re: Trigonometry

Hi!

For the first question, be careful, because the cosine rule is not like that... (maybe dividing all the terms in the rhs rather than only the last one) Calling the triangle sides a = AB, b = BC and c = CA, and the angle between a and c being alpha:

For the second question, I attach a diagram for what I understand it is described. The cosine rule can again be applied to the diagram, using exactly the same notation as above. Then we get:

Then, the distance is 3.32 + 3.2 + 2.5 = 9.02

Cheers
Jose

Last edited by juriguen (2009-09-21 07:57:45)

---

“Make everything as simple as possible, but not simpler.” -- Albert Einstein