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त्रिकोणमिति का परिचय

Question
CBSEHHIMAH10010239

मान निकालिए: 
sin space 25 degree space cos space 65 degree space plus space cos space 25 degree space sin space 65 degree

Solution

sin (90° - 65°). cos 65° + cos (90° - 65°). sin 65°
= cos65°. cos 65° + sin 65°. sin 65°
= cos2 65° + sin2 65° [∵ sin2 A + cos2 A = 1]
= 1.