IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => IGCSE/ GCSE => Math => Topic started by: anusha500 on May 11, 2009, 09:16:22 am

Title: math questions. =S
Post by: anusha500 on May 11, 2009, 09:16:22 am

i attached a question. i cant seem to get the same answer to part D. could someone else pls try.

another question.

find h.       2h=100/h^2

so u get (2h)*(h^2)=100
how do you simplify tht?
2h^3 or 2h^5 ?

Title: Re: math questions. =S
Post by: astarmathsandphysics on May 11, 2009, 09:38:15 am

2h^3=100 so h^3=50 so h=cube root of 50

Use cosine rule to find AD
AD²=8^2+7^2-2*8*7*cos80=93.55 so  AD=9.67
Then cut OAD  into 2 right angled triangles with angles 80 at centre. trig gives r=4.836/sin80=4.91

Title: Re: math questions. =S
Post by: SGVaibhav on May 11, 2009, 09:43:33 am

why not sine rule

plus my answer is coming 4.90 using trigonometry and sine rule.

how?

Title: Re: math questions. =S
Post by: astarmathsandphysics on May 11, 2009, 09:44:18 am

2h^3=100 so h^3=50 so h=cube root of 50

Use cosine rule to find AD
AD²=8^2+7^2-2*8*7*cos80=93.55 so  AD=9.67
Then cut OAD  into 2 right angled triangles with angles 80 at centre. trig gives r=4.836/sin80=4.91
Think their answer must be wrong. Examined everything.

Title: Re: math questions. =S
Post by: SGVaibhav on May 11, 2009, 09:48:49 am

now its time to show off!!  [party time]
 8)

now i wonder how can I and Mr. Paul be wrong

Title: Re: math questions. =S
Post by: SGVaibhav on May 11, 2009, 09:49:17 am

after all the question was wrong