Question

Evaluate without using the trigonometrical tables :
sin 22degrees - cos 68degrees +cos 25degrees . cos 65degrees - sin 25degrees . sin 65degrees

Answer 1

Answer:

0

Step-by-step explanation:

sin22° - cos68° + cos25° . cos65° - sin25° . sin65°

= sin(90° - 68°) - cos68° + cos(90° - 65°) . cos65° - sin(90° - 65°) . sin65°

[We know that sin(90° - Ф) = cosФ and cos(90° - Ф) = sinФ]

= cos68° - cos68° + sin65°.cos65° - cos65° . sin65°

= 0