IIT JEE , AIEEE Forum - Mathematics , Differential Calculus

ram_ram

the diffrenece between the greatest and least values of the function

f(x)= cos x +1/2 cos 2x - 1/3 cos 3x is

A 2/3

b 8/7

c 9/4

3/8

q-2 a straight line through the point (h,k) where h greater than 0

and k is grteater makes positive intercept on the co- ordinate axes then the minimum lenght of the line intercepted between the co- ordinate axes is

-------------------------- ans?

ram_ram

well m new here

so is is there ne other way to ask

cz by this way no1 is ansering

pavanholla

d first 1s d same. diffrenciation & substitution of all critical pts

pavanholla

m 2 is a new kid on d block.well not anymore intrested of status bcos it hardly matters

shipra22_bhardwaj

hii ram

see

clearly f(x) is a perodic func with peroid 2 pie

so the diffrence between the graetest and least values of the func f(x) is the diffrence between grtest nd least values on the interval [0, 2 pie]

we have

f'(x) = - (sin x + sin2x - sin3x )

= -( 2 sin3x/2 cosx/2 - 2 sin3x/2 cos 3x/2 )

= - 4 sinx/2 sin3x/2 sinx

so f'(x) = 0 so x= 0, 2pie /3 , pie and 2pie

now f(0) = 1 +1/2 - 1/3 = 7/6

f(2pie/3)= -13/12

f(pie)= - 1/6

f(2pie)- 7/6

the largest and smallest of these values are 7/6 and - 13/ 12

so diffrence = 9/4

correct me if m rong

ram_ram

thanx shipra

u r absolutly rite

do u have rd sharma objec

ram_ram

well i know its not de place to ask this

but still plz tell me

is bsc is equlvalent to btech

or bsc+ msc

wat r de scopes after bsc nd msc

dragon_thedanger

no not at all.

bsc is meant for research work.ucan make ur carrier in teaching and civil services by bsc but there is not ample scope in engineering .