大学数学 求高手帮忙
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大学数学 求高手帮忙
z = (3+4i)^3(4-3i)^2/(3-4i)^5
= (3+4i)^3(4-3i)^2(3+4i)^5/(3*3+4*4)^5
= (3+4i)^8(4-3i)^2/5^(10)
= (3+4i)^6[(3+4i)(4-3i)]^2/5^(10)
= (3+4i)^6*(-i)^2[(3+4i)(3-4i)]^2/5^(10)
= -(3+4i)^6*5^4/5^(10)
= -(3+4i)^6/5^6
= -(3/5 + 4i/5)^6
记cos(A) = 3/5, sin(A) = 4/5,
则
z = -[cos(A) + isin(A)]^6
= -[cos(6A) + isin(6A)]
|z| = { [-cos(6A)]^2 + [-sin(6A)]^2 }^(1/2) = 1^(1/2) = 1
= (3+4i)^3(4-3i)^2(3+4i)^5/(3*3+4*4)^5
= (3+4i)^8(4-3i)^2/5^(10)
= (3+4i)^6[(3+4i)(4-3i)]^2/5^(10)
= (3+4i)^6*(-i)^2[(3+4i)(3-4i)]^2/5^(10)
= -(3+4i)^6*5^4/5^(10)
= -(3+4i)^6/5^6
= -(3/5 + 4i/5)^6
记cos(A) = 3/5, sin(A) = 4/5,
则
z = -[cos(A) + isin(A)]^6
= -[cos(6A) + isin(6A)]
|z| = { [-cos(6A)]^2 + [-sin(6A)]^2 }^(1/2) = 1^(1/2) = 1