Answer:
fourth option
Step-by-step explanation:
Using the trigonometric identity
cos²x + sin²x = 1
Divide all terms by cos²x
+
=
which gives
1 + tan²x = sec²x
By letting

we get derivatives


a) Substitute these into the differential equation. After a lot of simplification, the equation reduces to

Examine the lowest degree term
, which gives rise to the indicial equation,

with roots at r = 0 and r = 4/5.
b) The recurrence for the coefficients
is

so that with r = 4/5, the coefficients are governed by

c) Starting with
, we find


so that the first three terms of the solution are

Answer:
a.bh/2
b.b=A×2/h
c.12
Step-by-step explanation:
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