If cos 9α = sinα and 9α < 90°, then the value of tan5α is
If cos 9α = sinα and 9α < 90°, then the value of tan5α is

(A) 1/√3 (B) √3 (C) 1 (D) 0

(C) 1

As indicated by the inquiry,

    \[cos\text{ }9\propto =\text{ }sin\propto and\text{ }9\propto <90{}^\circ \]

for example 9α is an intense point

We realize that,

    \[sin\left( 90{}^\circ -\theta  \right)\text{ }=\text{ }cos\text{ }\theta \]

In this way,

    \[cos\text{ }9\propto =\text{ }sin\text{ }\left( 90{}^\circ -\propto  \right)\]

Since,

    \[cos\text{ }9\propto =\text{ }sin\left( 90{}^\circ -9\propto  \right)\text{ }and\text{ }sin\left( 90{}^\circ -\propto  \right)\text{ }=\text{ }sin\propto \]

Subsequently, sin (90°-9∝) = sin∝

    \[90{}^\circ -9\propto =\propto \]

10∝ = 90°

∝ = 9°

Subbing ∝ = 9° in tan 5∝, we get,

    \[tan\text{ }5\propto =\text{ }tan\text{ }\left( 5\times 9 \right)\text{ }=\text{ }tan\text{ }45{}^\circ =\text{ }1\]

∴, tan 5∝ = 1