Sina^2+cosa^2=1
sin^2+(4|5)^=1
sin^2+16|25=1
sin^2=1-16|25
sin^2=25|25-16|25
sin^2=9|25
sin=3/5
ctg=cosa|sina=4|5:3|5=4/3
tg=sin|cos=3|5:4|5=3|4
40100000005...................,.,.
( 3x - 1 )/4x + ( 2x + 3 )/( x - 4 ) = ( ( 3x - 1 )( x - 4 ) + 4x( 2x + 3 )) / ( 4x( x - 4 )) = ( 3x² - 12x - x + 4 + 8x² + 12x ) / ( 4x² - 16x ) = ( 11x² - x + 4 ) / ( 4x² - 16x )