Question:

In each of the following cases find the least positive value of $\displaystyle \alpha$ for which:

$\displaystyle \cos ( \alpha-\theta )^o = \sin \theta^o $

Attempt:

Don't know how to get the value of $\displaystyle \alpha$ (Sadsmile)

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- Apr 12th 2008, 02:46 AMlooi76[SOLVED] Trignometry Help
**Question:**

In each of the following cases find the least positive value of $\displaystyle \alpha$ for which:

$\displaystyle \cos ( \alpha-\theta )^o = \sin \theta^o $

**Attempt:**

Don't know how to get the value of $\displaystyle \alpha$ (Sadsmile) - Apr 12th 2008, 03:21 AMMoo
Hello,

Once again use the formula :

cos(a-b)=cos(a)cos(b)+sin(a)sin(b)

So you will have to find $\displaystyle \alpha$ such as $\displaystyle \cos(\alpha)=0$ and $\displaystyle \sin(\alpha)=1$ as this relation has to be true for any $\displaystyle \theta$