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Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: T.Q on January 04, 2010, 02:21:56 pm

Title: NEED C3 HEELP
Post by: T.Q on January 04, 2010, 02:21:56 pm

(ii) Solve

  8 cot X – 3 tan X = 2,

for 0 < X < 90, giving your answer to 1 decimal place.   (5)


   SHOW  YOUR WORKING PLZ

Title: Re: NEED C3 HEELP
Post by: vanibharutham on January 04, 2010, 02:45:49 pm

8cotx - 3tanx - 2 = 0
8/tanx -3tanx - 2 = 0

Multiply tan x on both sides,
this gives:

8 - 3 tan²x - 2tanx = 0

3tan²x+ 2tanx - 8 = 0

solve the quadratic

(3 tan x - 4) ( tan x + 2)

tan x = 4/3     and tan x = -2

x = 53.1 , -63.4

therefore,
x = 53.1, 116.6

but in the range,

x = 53.1 only

Title: Re: NEED C3 HEELP
Post by: T.Q on January 04, 2010, 02:53:15 pm

Quote from: vanibharutham on January 04, 2010, 02:45:49 pm

8cotx - 3tanx - 2 = 0
8/tanx -3tanx - 2 = 0

Multiply tan x on both sides,
this gives:

8 - 3 tan²x - 2tanx = 0

3tan²x+ 2tanx - 8 = 0

solve the quadratic

(3 tan x - 4) ( tan x + 2)

tan x = 4/3     and tan x = -2

x = 53.1 , -63.4

therefore,
x = 53.1, 116.6

but in the range,

x = 53.1 only

thank you :)