Saved Bookmarks
| 1. |
\sin 65^{\circ}+\cos 65^{\circ}=\sqrt{2} \cos 20^{\circ} |
|
Answer» For RHS√2 cos20 = √2 cos (65 - 45) =√2cos65 cos45 +√2 sin65 sin45 =√2 cos65 (1/√2) + √2 sin65 (1/√2) => cos65 + sin65 = √2 cos20° => sin65 + cos65 = √2 cos20 Hence, proved. We used the identity rule - cos (A - B) = cosA cosB + sinA sinB |
|