A glass prism of angle A = 6 0 ^ ∘ gives a minimum angle of...

\mu = \text\sin \left(\dfrac{\delta + \text{A}}{2}\right)\left(\text\sin\left(\dfrac{A}{2}\right)\right), where \delta is the minimum deviation<br /><br />\dfrac{\text{d}\mu}{dδ} = \dfrac{\cos \left(\dfrac{\delta + A}{2}\right)}{\text{2sin}\left(\dfrac{A}{2}\right)}</p><p>⇒ \dfrac{\text{d}\mu}{μ} = \dfrac{\text\cos\left(\dfrac{\delta + A}{2}\right)}{\text{2sin}\left(\dfrac{\delta + A}{2}\right)} d$\delta<br /><br />$⇒ \dfrac{\text{d}\mu}{μ} = \dfrac{1}{2}\text\cot\left(\dfrac{\delta + A}{2}\right)\text{d \delta}</p><p> \text{ and } \text{ and } \text{ and } \text{ and } \left(\dfrac{\delta + A}{2}\right) =45 °

⇒ \dfrac{\text{d}\mu}{μ} \times100 = \dfrac{1}{2}\text\cot \left(45 °\right)\dfrac{\pi}{180}\text{\times 100}

Percentage error= \dfrac{5 \pi}{1 8} \text{%}