If sin (x + iy) sin (@+ i&) = 1, show that
(i) tanh² y cosh² & = cos@
(ii) tanh² &cosh² y = cos x.
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Suppose the loan is cleared in n months. Clearly, the amounts form an A.P. with first term 20 and the common difference 15.
∴ Sum of the amounts =3250
⟹
2
n
{2×20+(n−1)×15}=3250
⟹
2
n
(40+15n−15)=3250
⟹n(15n+25)=6500
⟹15
2
+25n−6500=0
⟹3n
2
+5n−1300=0
⟹(n−20)(3n+65)=0
⟹n=20 or, n=−
3
65
⟹n=20 [∵n
=
3
65
]
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