Question

. ம‌தி‌ப்‌பு கா‌ண்க

(cos35°)/(sin55°)+(sin12°)/(cos78°)-(cos18°)/(sin72°)

Answer 1

விளக்கம்:

$\frac{\cos 35^{\circ}}{\sin 55^{\circ}}+\frac{\sin 12^{\circ}}{\cos 78^{\circ}}-\frac{\cos 18^{\circ}}{\sin 72^{\circ}}$   ன் மதிப்பு

$=\frac{\cos 90^{\circ}-55^{\circ}}{\sin 55^{\circ}}+\frac{\sin \left(90^{\circ}-78^{\circ}\right)}{\cos 78^{\circ}}-\frac{\cos \left(90^{\circ}-72^{\circ}\right)}{\sin 72^{\circ}}$

$[\cos 35^{\circ}=\cos \left(70^{\circ}-55^{\circ}\right)]$

$=\frac{\sin 55^{\circ}}{\sin 55^{\circ}}+\frac{\cos 78^{\circ}}{\cos 78^{\circ}}-\frac{\sin 72^{\circ}}{\sin 72^{\circ}} \sin 12^{\circ}$

$=\sin \left(90^{\circ}-78^{\circ}\right)$

$=1+1+(-1)=1$

$\left.\cos 18^{\circ}=\cos \left(90^{\circ}-72^{\circ}\right)\right$.