1+sin^2x + 5 cos x - 4 = 0

Question

1+sin^2x + 5 cos x - 4 = 0

Answer 1

1+sin^2х+5cosx-4=0
1+(1-cos^2x)+5cosx-4=0
-cos^2x+5cosx-4=0
cos^2x-5cosx+4=0
Пусть cosx=t, тогда
t^2-5t+4=0
D=25-4*1*4=25-16=9
t1=5+3/2=4
t2=5-3/2=2

Comments

во второй строчке 1*(1-cos^2x)+5cosx-4=0