C C.C. New member Joined Nov 14, 2009 Messages 2 Nov 14, 2009 #1 I really need help with this integration problem. I have so far: (1-sinx^2)^2 * cosx * tanx^2 * tan x) But how do I continue?
I really need help with this integration problem. I have so far: (1-sinx^2)^2 * cosx * tanx^2 * tan x) But how do I continue?
D Deleted member 4993 Guest Nov 14, 2009 #2 C.C. said: I really need help with this integration problem. I have so far: (1-sinx^2)^2 * cosx * tanx^2 * tan x) But how do I continue? Click to expand... Use \(\displaystyle tan^3(x) = \frac{sin^3(x)}{cos^3(x)}\)
C.C. said: I really need help with this integration problem. I have so far: (1-sinx^2)^2 * cosx * tanx^2 * tan x) But how do I continue? Click to expand... Use \(\displaystyle tan^3(x) = \frac{sin^3(x)}{cos^3(x)}\)
C C.C. New member Joined Nov 14, 2009 Messages 2 Nov 14, 2009 #3 Alright, I used that and got: INTEGRAL (1-(sinx)^2)^2 * cosx * (sinx)^3/(cosx)^3 (du/cosx) = dx INTEGRAL (1-u^2)^2 * (u^3/(cosx)^3) (1-u^2)^2 == 1 INTEGRAL 1 * u^3 * (1/(cosx)^3) Is this right so far?
Alright, I used that and got: INTEGRAL (1-(sinx)^2)^2 * cosx * (sinx)^3/(cosx)^3 (du/cosx) = dx INTEGRAL (1-u^2)^2 * (u^3/(cosx)^3) (1-u^2)^2 == 1 INTEGRAL 1 * u^3 * (1/(cosx)^3) Is this right so far?
B BigGlenntheHeavy Senior Member Joined Mar 8, 2009 Messages 1,577 Nov 15, 2009 #4 \(\displaystyle \int cos^{5}(x)tan^{3}(x)dx \ = \ \int cos^{5}(x)\frac{sin^{3}(x)}{cos^{3}(x)}dx \ = \ \int cos^{2}(x)sin^{3}(x)dx.\) \(\displaystyle = \ \int cos^{2}(x)sin^{2}(x)sin(x)dx \ = \int cos^{2}(x)sin(x)[1-cos^{2}(x)]dx\) \(\displaystyle = \ \int [cos^{2}(x)sin(x)-cos^{4}(x)sin(x)]dx \ = \ \int cos^{2}(x)sin(x)dx-\int cos^{4}(x)sin(x)dx\) \(\displaystyle You \ should \ be \ able \ to \ take \ it \ from \ here.\)
\(\displaystyle \int cos^{5}(x)tan^{3}(x)dx \ = \ \int cos^{5}(x)\frac{sin^{3}(x)}{cos^{3}(x)}dx \ = \ \int cos^{2}(x)sin^{3}(x)dx.\) \(\displaystyle = \ \int cos^{2}(x)sin^{2}(x)sin(x)dx \ = \int cos^{2}(x)sin(x)[1-cos^{2}(x)]dx\) \(\displaystyle = \ \int [cos^{2}(x)sin(x)-cos^{4}(x)sin(x)]dx \ = \ \int cos^{2}(x)sin(x)dx-\int cos^{4}(x)sin(x)dx\) \(\displaystyle You \ should \ be \ able \ to \ take \ it \ from \ here.\)