The Exact Value of cos 18 degrees.

The exact value of cos 18deg = √[(10+2√5)]/4 can be solve by using the Pythagorean Theorem Relation cos theta = √[1 - (sin theta)^2], where theta = 18deg, or cos 18deg = √[1 - (sin 18deg)^2]. Substitute the exact value of sin 18deg = (√5-1)/4 to the formula, in which I've already solved above and included in this playlist. Evaluate and simplify.

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Differential Calculus    • Prove f'(x) = nx^(n-1), if f(x) = x^n...  

Complex Numbers    • Prove:⁡⁡  (a⁡+⁡b⁡i)(c⁡+⁡d⁡i)⁡ = ⁡(ac⁡...  

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