Question

MA
Find the value:
(i) sin 78º – sin 18° + sin 30° – sin 42°​

Answer 1

Answer:

Hope it helps!! Mark this answer as brainliest if u found it useful and follow me for quick and accurate answers...

Step-by-step explanation:

sin78-sin18+sin30-sin42

= sin78-sin42-sin18+sin30

= 2cos(120/2).sin18-sin18+sin30

= 2cos60.sin18-sin18+sin30

= (2×1/2).sin18-sin18+sin30

= sin18-sin18+1/2

=1/2

Answer 2

Answer:

If A+B=90

∘

, then

sinAsecB

tanA.tanB+tanAcotB

−

cos

2

A

sin

2

B

=tanA

View Answer

2cos

2

A

=±

1−sinA

±

1+sinA

, when

2

A

=−140

∘