15cos2t+8sint=9 1<t<3
15*(1-2sin^2t)+8sint=9
15-30sin^2t+8sint=9
sin^2t=x
15-30x^2+8x=9
-30x^2+8x+15-9=0
-30x^2+8x+6=0
-15x^2+4x+3=0
15x^2-4x-3=0
D=16+12*15=14^2
x=(4+14)/30=18/30
x=(4-14)/30=-1/3
sin^2t=-1/3 ne zadovilna
sin^2t=18/30
sint=+-sqrt(18/30)
t=(-1)^n*arcsin(+-sqrt(18/30))+2pin;nEz;
Вот решение.надеюсь помог:)
X²<span>-3x-40=0
d = b</span>² -4ac = 9 - 4 * (-40) = 9 + 160 = 169
√d = √169 = 13
<u>x₁</u> = ( -b + √d ) / 2a = ( 3 + 13 ) / 2 = 16 / 2 = 8
<u>x₂</u> = ( -b - √d ) / 2a = ( 3 - 13 ) / 2 = -10 / 2 = -5
У=72-2√х^2
у=72-2|х|
2|х|=72-у