(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Without using tables(calculators) find the numerical value of

Sin[Pi/8]^2 - Cos[3 (Pi/8)]^4

2. Relevant equations

3. The attempt at a solution

I tried changing it to:

1-cos[pi/8]^2 - cos[3pi/8]^4 but have no idea where to go... its really got me scratching my head.

Any ideas? Any help is much appreciated, thank you.

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# Homework Help: Trigonometric Identities

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