Question

), If Sin3A=1 and O< A,< 90 find
b) cosA​

Answer 1

Question:

$If sin\:3\theta = 1 ; where 0 < \theta < 90°$$Then\:Find$

$(i) Cos\:\theta$

To Find:

$\underline{\underline{Cos \theta}}$

We Know:

$Sin 90° = 1$

$Cos 30° = \dfrac{\sqrt{3}}{2}$

Solution:

By solving this :

$If sin\:3\theta = 1 ; where 0 < \theta < 90°$

By putting sin 90° instead of 1.

$\Rightarrow sin\:3\theta = sin 90°$

Sin and sin will cross with each other..

$\Rightarrow 3\theta = 90°$

$\Rightarrow \theta = \dfrac{90°}{3}$

$\Rightarrow \theta = 30°$

${\boxed{\therefore \theta = 30° }}$

By putting the value of theta in the equation.

$(i) cos \theta = ?$

${\boxed{\theta = 30°}}$

$\Rightarrow Cos 30° = \dfrac{\sqrt{3}}{2}$

$\therefore Cos 30° = \dfrac{\sqrt{3}}{2}$