Turn on thread page Beta
    • Thread Starter
    Offline

    1
    ReputationRep:
    Hello. I am stuck on this trig question.
    The triangle ABC, shown in the diagram, is such that AB=5cm, AC=8cm,BC=10cm and angle BAC=Theta.
    Show that Theta=97.9, correct to the nearest 0.1 degrees.
    Any help would be appreciated
    Offline

    3
    ReputationRep:
    (Original post by WhiteTigerKURD)
    Hello. I am stuck on this trig question.
    The triangle ABC, shown in the diagram, is such that AB=5cm, AC=8cm,BC=10cm and angle BAC=Theta.
    Show that Theta=97.9, correct to the nearest 0.1 degrees.
    Any help would be appreciated
    Remember this formula or did you forget?

     Cos \theta = \frac{b^2 + c^2 - a^2}{2bc}
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by LelouchViRuge)
    Remember this formula or did you forget?

     Cos \theta = \frac{b^2 + c^2 - a^2}{2bc}
    Oh, I forgot about that. Thank you✌️✌
    Offline

    3
    ReputationRep:
    (Original post by WhiteTigerKURD)
    Oh, I forgot about that. Thank you✌️✌
    Are you doing Edexcel?

    If so, you'll be given this in the formula booklet:  a^2 = b^2 + c^2 - 2bcCosA

    This can just be rearranged for  Cos A

     2bcCosA + a^2 = b^2 + c^2

     2bcCosA = b^2 + c^2 - a^2

     Cos A = \frac{b^2 + c^2 - a^2}{2bc}

    Remember this bra ^^
 
 
 
The home of Results and Clearing

1,082

people online now

1,567,000

students helped last year

University open days

  1. University of Buckingham
    Postgraduate Open Evening Postgraduate
    Thu, 23 Aug '18
  2. University of Glasgow
    All Subjects Undergraduate
    Tue, 28 Aug '18
  3. University of Aberdeen
    Undergraduate Open Day Undergraduate
    Tue, 28 Aug '18
Poll
How are you feeling about GCSE results day?
Help with your A-levels

All the essentials

The adventure begins mug

Student life: what to expect

What it's really like going to uni

Rosette

Essay expert

Learn to write like a pro with our ultimate essay guide.

Uni match

Uni match

Our tool will help you find the perfect course for you

Study planner

Create a study plan

Get your head around what you need to do and when with the study planner tool.

Study planner

Resources by subject

Everything from mind maps to class notes.

Hands typing

Degrees without fees

Discover more about degree-level apprenticeships.

A student doing homework

Study tips from A* students

Students who got top grades in their A-levels share their secrets

Study help links and info

Can you help? Study help unanswered threadsRules and posting guidelines

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.