(a^x)*(a^x)=a^(x+x)？
(a^x)/(a^x)=a^(x-x)？
a=(a^x)^ 1/x
In the same way; In a similar way
? a^x=M^y
? a^x=m^(y-(y- 1))*m^(y- 1)
Substitute m y = a x into the corresponding item on the left,
m^y=m^(y-(y- 1))*m^(y- 1)
? M^y/M^(y- 1)=M^ 1
? M (y-(y- 1)) = m (then use the third exponential algorithm).
[(m^y)^ 1/y]^(y-(y- 1))=m
Substitute m y = a x into the corresponding item on the left,
[(a^x)^ 1/y]^(y-(y- 1))=m
? (a^x)^( 1/y)=M
? a^(x/y)=M
Prove completion.
With point d as DE⊥AB in e,
And DC⊥CB, AB⊥CB,
∴∠DEB=∠ABC=∠DCB=90，
∴ Quadrilateral DEBC is a rectangle,
In Rt△ADE, ∠ α = 43, DE = CB =139m.