Question

sin⁴a+cos⁴a, если sina-cosa=0.5

Answer 1

Ответ:

$sina-cosa=0,5\\\\(sina-cosa)^2=0,25\\\\\underbrace{sin^2a+cos^2a}_{1}-2\, sina\cdot cosa=0,25\\\\2sina\cdot cosa=1-0,25\\\\2sina\cdot cosa=0,75\ \ \ \to \ \ \ \underline {sina\cdot cosa=0,375}\\\\\\(\underbrace {sin^2a+cos^2a}_{1})^2=1^2=1\ \ \ \Rightarrow \ \ \\\\sin^4a+cos^4a+2sin^2a\cdot cos^2a=1\\\\sin^4a+cos^4a=1-2sin^2a\cdot cos^2a\\\\sin^4a+cos^4a=1-2\cdot (0,375)^2\\\\sin^4a+cos^4a=1-0,28125\\\\\underline {sin^4a+cos^4a=0,71875\ }$