Question

Find the value of cos35\sin55+sin12\cos78-cos 18\72​

Answer 1

Step-by-step explanation:

By selling 90 ball pens for rupees 180, a person loses 20%. How many ball pens should he sell for rupees 96, so as to have a gain of 20%?

Answer 2

Answer:

$\frac{cos \: 35}{sin \: 55} + \frac{sin \: 12}{cos \: 78} - \frac{cos \: 18}{sin \: 72} = 1$

Step-by-step explanation:

$\frac{cos \: 35}{sin \: 55} + \frac{sin \: 12}{cos \: 78} - \frac{cos \: 18}{sin \: 72}$

$= \frac{sin(90 - 35)}{sin \: 55} + \frac{cos \: (90 - 12)}{cos \: 78} - \frac{sin(90 - 18)}{sin \: 72}$

$= \frac{sin \: 55}{sin \: 55} + \frac{cos \: 78}{cos \: 78} - \frac{sin \: 72}{sin \: 72}$

$= 1 + 1 - 1$

$= 2 - 1$

$= 1$