Question

ПОМОГИТЕ!!!!!!!!!!!!!!Срочно!!!!!!!!!!!!!!!!!!!!ПЛИЗ!!!!!!!!!!!!!!!!!!!

Answer 1

B1. sinα <0 при α∈(π/2,π)
sin²α=1-cos²α=1-(-√21/5)²=1-21/25=(25-21)/25=4/25
sinα=-2/5
B2
$28 sqrt{6}cos frac{pi}{6} cos frac{5pi}{4} =28 sqrt{6}cos frac{pi}{6} (-cos frac{pi}{4})= -28 sqrt{6}frac{ sqrt{3} }{2} frac{ sqrt{2} }{2}=-7*6=-42$

B3. -21√3 tg(660°)=-21√3 tg(300°)=-21√3 tg(-60°)=21√3 tg(60°)=21√3 √3 =21*3=63
B4.
$30 sqrt{6}cos(- frac{pi}{4}) sin(- frac{pi}{3}) = 30 sqrt{6}cos(frac{pi}{4}) (-sin( frac{pi}{3}))= \ =-30 sqrt{6}cos(frac{pi}{4}) sin( frac{pi}{3})=-30 sqrt{6} frac{ sqrt{2} }{2} frac{ sqrt{3} }{2} = -15*6/2=-45$
B5.
$frac{22(sin^272-cos^272)}{cos144}=-frac{22(cos^272-sin^272)}{cos144}= -22frac{cos144}{cos144}=-22$
B6.
$frac{-51 sin385}{sin25}= frac{-51 sin(360+25)}{sin25}=frac{-51 sin25}{sin25}=-51$
B7.
$frac{3sin( alpha +pi)-2cos( frac{pi}{2}+ alpha ) }{sin( alpha -2pi)}=frac{3(-sin alpha)-2(-sinalpha ) }{sinalpha} =frac{-3sin alpha+2sinalpha }{sinalpha}=-1$
B8.
5sin²α +11cos²α = 9
5sin²α + 5cos²α + 6cos²α= 9
5 + 6cos²α= 9
6cos²α= 4
cos²α= 4/6
sin²α=1-cos²α=1-4/6=2/6
tg²α=sin²α/cos²α=(2/6):(4/6)=1/2

B9.
$frac{4sin alpha +2cos alpha }{5sin alpha -16cos alpha }=1 \ 4sin alpha +2cos alpha= 5sin alpha -16cos alpha$
4sinα+2cosα=5sinα-16cosα
sinα=18cosα
tgα=sinα/cosα=18

B10.
$4sin( alpha +pi)+7cos( frac{pi}{2}+ alpha )=-4sin alpha -7sin alpha =-11 sin alpha= \ =-11*0,25=-2,75$