Book: NCERT - Mathematics
Chapter: 8. Introduction to Trigonometry
Subject: Maths - Class 10th
Q. No. 3 of Exercise 8.4
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3
Evaluate:
(i) 
(ii) Sin 25° Cos 65° + Cos 25° Sin 65°
(i) [Sin263° + sin2 (90° -63°)]/ [coa217° + cos2 (90° -17)°]
Sin263° + cos2 (63°)/([cos217° + sin217°]
= 1
(ii) sin 25°cos 65°+ cos 25°sin 65°
= sin 25° cos (90°-25°) + cos 25°sin 65°
= sin2 25° + cos 25° cos (90°-25°)
= sin2 25° + cos2 25°
=1
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using the identity 
[Hint: Simplify LHS and RHS separately]