化简求值化简求值
[(1/(a+2)-a/(a^2+3a+2)]/[2/(4-a^2)]
={(1/(a+2)-a/[(a+2)(a+1)]}/{2/[(2+a)(2-a)]}
=[1-a/(a+1)]/[2/(2-a)]
=[1/(a+1)]/[2/(2-a)]
=(2-a)/(2a+2)
=(2-sin45+sin30)/(2sin45-2sin30+2)
=(2-2^1/2*0。 5+0。5)/(2*2^1/2*0。5-2*0。5+2)
=0。5*(5-2^1/2)/(2^1/2+1)
=0。5*(5-2^1/2)(2^1/2-1)
=3*2^1/2-3。5。全部
[(1/(a+2)-a/(a^2+3a+2)]/[2/(4-a^2)]
={(1/(a+2)-a/[(a+2)(a+1)]}/{2/[(2+a)(2-a)]}
=[1-a/(a+1)]/[2/(2-a)]
=[1/(a+1)]/[2/(2-a)]
=(2-a)/(2a+2)
=(2-sin45+sin30)/(2sin45-2sin30+2)
=(2-2^1/2*0。
5+0。5)/(2*2^1/2*0。5-2*0。5+2)
=0。5*(5-2^1/2)/(2^1/2+1)
=0。5*(5-2^1/2)(2^1/2-1)
=3*2^1/2-3。5。收起