Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    0
    ReputationRep:
    I need help answering a question:

    In triangle abc, cosA = 0.5, AB = 6cm, BC = 2x cm, AC = x cm, show that x^2 + 2x - 12 = 0
    Offline

    20
    ReputationRep:
    Hi Bethany, this question might be better in the Maths forum
    Offline

    3
    ReputationRep:
    (Original post by Bethanyt5560)
    I need help answering a question:

    In triangle abc, cosA = 0.5, AB = 6cm, BC = 2x cm, AC = x cm, show that x^2 + 2x - 12 = 0
    COSINE RULE
    You know how to use the cosine rule?
    i.e.  a^2 = b^2 + c^2 -2bc \cos A

    Draw out the triangle ABC.
    Put the lengths given in the question.

    You'll notice that 2x is opposite angle A.
    And you're given cos A.

    So start subbing the appropriate values into the cosine rule, and then reduce it to the quadratic given.
 
 
 
Poll
Do you agree with the PM's proposal to cut tuition fees for some courses?
Useful resources
AtCTs

Ask the Community Team

Got a question about the site content or our moderation? Ask here.

Welcome Lounge

Welcome Lounge

We're a friendly bunch. Post here if you're new to TSR.

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.