How to develop a formula for cos3x?

Hello, I need some help on how to express cos 3x in terms of cos x. I realize that you need to use double angle formulas, but I'm not able to group the terms properly in the second step and need some help in finding the final answer. Thanks in advance...

Given that Venus’ sidereal rotation period is 243.01 days and its orbital period is 224.70 days, develop a formula and use it to show that a solar day on Venus lasts 116.8 days. (Hint: the formula relating Venus’ solar day to its sidereal rotation period...

I'm not exactly sure if it would be a recursive formula, I can't develop one. The set of data starts at 2, so it looks like 2, 7, 15, 26, 40, 57, 77, 100, 126, etc. where at each interval, the amount added increases by 3. So from 2-7 is 5 7-15 is 8 ...

My son is 11 1/2 months, he uses Isomil Advance. His grandmother says one year then he can be off formula. I say about a year and a half, because babies still develop and need the vitamins and nurishment from the formula. When my daughter was a baby...

...such as a cleanser, deodorant, cologne, etc? My favorite cleanser that I've been using to keep my skin silky smooth for years (yes, The Nolte is vain) is suddenly causing my skin to appear blotchy and uneven. Is it possible to develop an allergy overnight...

My Labrador retriever recently developed the habit of eating things like dust from under the couches, chewing on socks, and eating grass. She is 10 years old and has never had this problem before. Recently, we switched her food formula to the one for...

Accept determinism as an axiom for a moment to extrapolate this idea. The alternative I'm considering--and preferring--is that humanity would develop in an alternative but formulaic manner. The formula being beyond human capacity--which is sort of a...