Re: Trigonometric function

Quote:

Originally Posted by

**Trefoil2727** 1. By squaring both sides of the identity sin^2 A + cos^2 A=1, or otherwise, show that sin^4 A + cos^4=(1/4)(3+cos4A). Hence find the possible greatest value and the smallest value of sin^4 θ + cos^4 θ

2. Given that A, B, C are the angles of a triangle, show that tan C= (tanA+tanB)/(tanAtanB-1)

What have you been able to do so far?

-Dan

Re: Trigonometric function

(sin^2 A + cos^2 A)^2 =1

sin^4 A + 2sin^2 A cos^2 A + cos^4 A =1

sin^4 A + cos ^4 A = 1- 2sin^2 A cos^2 A

that's all I can do..

For the second question, I really don't know where to start

Re: Trigonometric function

Quote:

Originally Posted by

**Trefoil2727** (sin^2 A + cos^2 A)^2 =1

sin^4 A + 2sin^2 A cos^2 A + cos^4 A =1

sin^4 A + cos ^4 A = 1- 2sin^2 A cos^2 A

that's all I can do..

For the second question, I really don't know where to start

Re: Trigonometric function

Hello, Trefoil2727!

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