Click to Chat

1800-1023-196

+91-120-4616500

CART 0

• 0

MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: Rs.

There are no items in this cart.
Continue Shopping
`        If x=cos55,y=cos65,z=cos175 then  what is the value of xy+yz+zx?`
2 years ago

Harshit
31 Points
```							= cos55cos65+cos175cos65+cos175cos55= cos65(cos55+cos175)+cos175cos55= cos65(2cos115cos65)+cos175cos55   [cosA+cosB=12cos( A+B/2 )cos( A-B/2 )]= cos65cos115+cos(180-5)cos55           [cos175=cos(180-5)=-cos5, cos60= ½ ]=cos65cos115-cos5cos55= ½ [2cos65cos115-2cos5cos55]= ½ [cos180+cos50-(cos60+cos50)]      [2cosAcosB=cos(A+B)cos(A-B)]= ½ [cos180-cos60]= ½ [0-½]= – ¼
```
2 years ago
Think You Can Provide A Better Answer ?

## Other Related Questions on Trigonometry

View all Questions »

### Course Features

• 731 Video Lectures
• Revision Notes
• Previous Year Papers
• Mind Map
• Study Planner
• NCERT Solutions
• Discussion Forum
• Test paper with Video Solution

### Course Features

• 31 Video Lectures
• Revision Notes
• Test paper with Video Solution
• Mind Map
• Study Planner
• NCERT Solutions
• Discussion Forum
• Previous Year Exam Questions