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Question-61165

Question Number 61165 by Tawa1 last updated on 29/May/19 Answered by MJS last updated on 30/May/19 $$\int\frac{\mathrm{cos}^{\mathrm{2}} \:\left(\mathrm{2}{x}−\mathrm{5}\right)\:\mathrm{cos}\:\left(\mathrm{2}{x}−\mathrm{14}\right)}{\mathrm{cos}\:\left(\mathrm{2}{x}−\mathrm{7}\right)}{dx}= \\ $$$$\:\:\:\:\:\left[{t}=\mathrm{2}{x}−\mathrm{7}\:\rightarrow\:{dx}=\frac{{dt}}{\mathrm{2}}\right] \\ $$$$=\frac{\mathrm{1}}{\mathrm{2}}\int\frac{\mathrm{cos}^{\mathrm{2}} \:\left({t}+\mathrm{2}\right)\:\mathrm{cos}\:\left({t}−\mathrm{7}\right)}{\mathrm{cos}\:\left({t}\right)}{dt}= \\ $$$$\:\:\:\:\:\left[\mathrm{use}\:\mathrm{these}:\right.…

if-x-y-z-are-three-distinct-complex-numbers-such-that-x-y-z-y-z-x-z-x-y-0-then-find-the-value-of-x-2-y-z-2-

Question Number 192160 by universe last updated on 10/May/23 $$\mathrm{if}\:\mathrm{x},\mathrm{y},\mathrm{z}\:\mathrm{are}\:\mathrm{three}\:\mathrm{distinct}\:\mathrm{complex}\:\mathrm{numbers} \\ $$$$\mathrm{such}\:\mathrm{that}\:\frac{\mathrm{x}}{\mathrm{y}−{z}}+\frac{\mathrm{y}}{\mathrm{z}−\mathrm{x}}+\frac{\mathrm{z}}{\mathrm{x}−\mathrm{y}}\:=\:\mathrm{0}\:\mathrm{then}\: \\ $$$$\mathrm{find}\:\mathrm{the}\:\mathrm{value}\:\mathrm{of}\:\:\Sigma\:\frac{\mathrm{x}^{\mathrm{2}} }{\left(\mathrm{y}−\mathrm{z}\right)^{\mathrm{2}} } \\ $$ Commented by mehdee42 last updated on 09/May/23…

show-that-f-x-y-0-x-y-0-0-x-2-y-x-6-2y-2-x-y-0-0-has-a-directional-derivative-in-the-direction-of-an-arbitrary-unit-vector-at-0-0

Question Number 192138 by Mastermind last updated on 09/May/23 $$\mathrm{show}\:\mathrm{that}\: \\ $$$$\mathrm{f}\left(\mathrm{x},\mathrm{y}\right)\:=\:\left\{_{\mathrm{0}\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\left(\mathrm{x},\mathrm{y}\right)=\left(\mathrm{0},\mathrm{0}\right)} ^{\frac{\mathrm{x}^{\mathrm{2}} \mathrm{y}}{\mathrm{x}^{\mathrm{6}} \:+\:\mathrm{2y}^{\mathrm{2}} }\:\:\:\:\:\:\:\:\:\:\:\:\left(\mathrm{x},\mathrm{y}\right)\neq\:\left(\mathrm{0},\mathrm{0}\right)} \right. \\ $$$$\mathrm{has}\:\mathrm{a}\:\mathrm{directional}\:\mathrm{derivative}\:\mathrm{in}\:\mathrm{the} \\ $$$$\mathrm{direction}\:\mathrm{of}\:\mathrm{an}\:\mathrm{arbitrary}\:\mathrm{unit}\:\mathrm{vector} \\ $$$$\phi\:\mathrm{at}\:\left(\mathrm{0},\mathrm{0}\right),\:\mathrm{but}\:\mathrm{f}\:\:\mathrm{is}\:\mathrm{not}\:\mathrm{continous}\:\mathrm{at}\:\left(\mathrm{0},\mathrm{0}\right)\: \\ $$…