\operatorname { sin } 35 ^ { \circ } \operatorname { sin } 55 ^ { \cir

1.	\operatorname { sin } 35 ^ { \circ } \operatorname { sin } 55 ^ { \circ } - \operatorname { cos } 35 ^ { \circ } \operatorname { cos } 55 ^ { \circ } = 0
Answer» Since cos (a+b) = - (sin a sinb - cos a cos b) so cos (35+55) = -(sin35 sin 55- cos 35 cos 55) so = - cos 90= 0 ѕιη35°×¢σѕ(90°-35°)-- ¢σѕ35°×ѕιη(90°-35°)=0ѕιη35°×1/ѕιη35°-- ¢σѕ35°×1/¢σѕ35°=01-1=00=0

\operatorname { sin } 35 ^ { \circ } \operatorname { sin } 55 ^ { \circ } - \operatorname { cos } 35 ^ { \circ } \operatorname { cos } 55 ^ { \circ } = 0

Answer»

Since cos (a+b) = - (sin a sinb - cos a cos b)

so cos (35+55) = -(sin35 sin 55- cos 35 cos 55)

so = - cos 90= 0

ѕιη35°×¢σѕ(90°-35°)-- ¢σѕ35°×ѕιη(90°-35°)=0ѕιη35°×1/ѕιη35°-- ¢σѕ35°×1/¢σѕ35°=01-1=00=0