Trig double angle equation help
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Hey /sci/, I'm studying for a math test and am seriously stumped at one problem.
Find the (real) values for A, B and C for all values of x:
I know to start by expanding (5cos(x)-9sin(x))^2 into 81sin^2(x)-90cos(x)sin(x)+25cos^2(x), and use the double angle formulas from there. I can get the value for B easily, 45*2cosxsinx=45sin2x, and since it's negative B must equal -45. But I keep ending up wrong with A and/or C.
I know which formulas to use, but I don't seem to get how to use multiple formulas simultaneously. Please help me, /sci/, I've been stuck on this part for over a week now.
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What do you guys think about mental medicine?
Not psychiatric stuff, but just using meditation to control and heal the body?
There seem to be many VERIFIED cases of people doing things like healing wounds, recovering from illnesses, surviving extreme temperatures and living to do it again, REPEATEDLY.
And ALL of them say it's just a skill they taught themselves through practice, training and meditation.
Some hard examples:
1)The placebo effect, which seems to make people healthier just by convincing them they will
2)some effects of mass hysteria, which can cause people to display the symptoms of diseases they don't have
3)Wim Hof, the guy climbed Mt. Kilimanjaro, submerged himself in ice water for over an hour and ran a marathon both above the artic circle AND in the Nairobi desert in nothing but shorts and sandals, all without any damage to his body or even discomfort.
What the hell is going on here?