Math Is Fun Forum

lkomarci

Member

Registered: 2005-08-24

Posts: 23

integrating trigonometric functions

i've been doing integrals of trig functions because it's my weakest point.
there are a few basic things that i don't understand.

for eg. i KNOW that:

sin^2x=(1-Cos2x)/2
cos^2x=(1+Cos2x)/2

but please explain this, why is...

1-(Cos^2)2x = 1-Cos4x

and

(Cos^3)2x = (1-(Sin^2)2x)Cos2x

lkomarci

Member

Registered: 2005-08-24

Posts: 23

Re: integrating trigonometric functions

whoops sorry it's supposed to say..
1-(Cos^2)2x = 1+Cos4x

tom a

Guest

Re: integrating trigonometric functions

i've been doing integrals of trig functions because it's my weakest point.
there are a few basic things that i don't understand.

for eg. i KNOW that:

sin^2x=(1-Cos2x)/2
cos^2x=(1+Cos2x)/2

but please explain this, why is...

1-(Cos^2)2x = 1-Cos4x

and

(Cos^3)2x = (1-(Sin^2)2x)Cos2x

maths drags

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: integrating trigonometric functions

Pythagoras' Theorem

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X'(y-Xβ)=0

lkomarci

Member

Registered: 2005-08-24

Posts: 23

Re: integrating trigonometric functions

i understand now, i borrowed some books from a local library and now i understand.
thank you George

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: integrating trigonometric functions

never mind, a systematic book is really helpful, hehe.

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X'(y-Xβ)=0