If tan^2theta = 1 - a^2tan2θ=1a2, then sectheta + tan^3thetacsctheta = (2 - a^2)^nsecθ+tan3θcscθ=(2a2)n. What is the value of nn?

4 Answers
Nov 29, 2016

1.51.5

Explanation:

a^2 = 1 - tan^2thetaa2=1tan2θ

Substitute:

sectheta + tan^3thetacsctheta = (2 - (1 - tan^2theta))^nsecθ+tan3θcscθ=(2(1tan2θ))n

Apply the following identities:

•secbeta = 1/cosbetasecβ=1cosβ
•tan beta = sinbeta/cosbetatanβ=sinβcosβ
•cscbeta = 1/sinbetacscβ=1sinβ

1/costheta + sin^3theta/cos^3theta xx 1/sintheta = (2 - (1 - tan^2theta))^n1cosθ+sin3θcos3θ×1sinθ=(2(1tan2θ))n

1/costheta + sin^2theta/cos^3theta = (1 + tan^2theta)^n1cosθ+sin2θcos3θ=(1+tan2θ)n

Put the left hand side on a common denominator and apply the identity 1 + tan^2beta = sec^2beta1+tan2β=sec2β.

(cos^2theta + sin^2theta)/cos^3theta = (sec^2theta)^ncos2θ+sin2θcos3θ=(sec2θ)n

Use the identity sin^2beta + cos^2beta = 1sin2β+cos2β=1.

1/cos^3theta = (sec^2theta)^n1cos3θ=(sec2θ)n

sec^3theta = (sec^2theta)^nsec3θ=(sec2θ)n

We can call sectheta = xsecθ=x.

x^3 = (x^2)^nx3=(x2)n

x^3 = x^(2n)x3=x2n

3 = 2n3=2n

n = 1.5n=1.5

Hopefully this helps!

Nov 29, 2016

3/232 and theta in Q_1θQ1.

Explanation:

Let t = tan thetat=tanθ. Then. t^2=1-a^2>=0 to |a|<=1t2=1a20|a|1

Now,

sec theta+tan^3theta csc thetasecθ+tan3θcscθ

=+-sqrt(1+t^2)+t^3(+-sqrt(I+1/t^2))=±1+t2+t3(±I+1t2)

=+-sqrt(1+t^2)(1+-t^2)=±1+t2(1±t2)

=+-(1+t^2)^(3/2)=±(1+t2)32, for + sign in the second factor ( csc theta > 0cscθ>0)

=+-(2-a^2)^(3/2 )=±(2a2)32, - sign is taken when sec theta < 0secθ<0

=(2-a^2)^n to sec theta > 0 and=(2a2)nsecθ>0and

n=3/2n=32 and csc theta >0 to theta in Q_1#.

I am sorry that I have involved +-±. But, this is Mathematics.

I have obtained an enforcing result theta in Q_1θQ1.

Nov 29, 2016

n = 3/2n=32

Explanation:

1/costheta+sin^3theta/cos^3theta 1/sintheta=1/costheta(1+tan^2theta)=(2-a^2)^n1cosθ+sin3θcos3θ1sinθ=1cosθ(1+tan2θ)=(2a2)n

then

costheta=(2-a^2)/(2-a^2)^n=(2-a^2)^(-(n-1))cosθ=2a2(2a2)n=(2a2)(n1)

squaring

cos^2theta=(2-a^2)^(-2(n-1))cos2θ=(2a2)2(n1)

but from tan^2theta=(1-a^2)->cos^2theta=(2-a^2)^(-1)tan2θ=(1a2)cos2θ=(2a2)1

arriving at

(2-a^2)^(-2(n-1))=(2-a^2)^(-1)(2a2)2(n1)=(2a2)1 so

2(n-1)=1->n=3/22(n1)=1n=32

Nov 29, 2016

Given

tan^2theta=1-a^2tan2θ=1a2

1+tan^2theta=1+1-a^21+tan2θ=1+1a2

sec^2theta=2-a^2sec2θ=2a2

Now
sectheta+tan^3thetacsctheta=(2-a^2)^nsecθ+tan3θcscθ=(2a2)n

=>sectheta+tan^3thetaxx1/sintheta=(2-a^2)^nsecθ+tan3θ×1sinθ=(2a2)n

=>sectheta(1+tan^3thetaxxcostheta/sintheta)=(2-a^2)^nsecθ(1+tan3θ×cosθsinθ)=(2a2)n

=>sectheta(1+tan^3thetaxx1/tantheta)=(sec^2theta)^nsecθ(1+tan3θ×1tanθ)=(sec2θ)n

=>sectheta(1+tan^2theta)=(sec^2theta)^nsecθ(1+tan2θ)=(sec2θ)n

=>secthetaxxsec^2theta=sec^(2n)thetasecθ×sec2θ=sec2nθ

=>sec^3theta=sec^(2n)thetasec3θ=sec2nθ

=>2n=32n=3

:.n=3/2