Question

How to find the exact value of sin50 cos40 + sin40cos50?

Answer 1

\(\sin (\alpha + \beta) = \sin \alpha \cos \beta + \sin \beta \cos \alpha \)

Answer 2

That is the angle addition formula for sine.

Answer 3

Please, elaborate it. :(

Answer 4

Use the formula above and replace every alpha with 50 and every beta with 40.
What do you get?

Answer 5

sin90

Answer 6

\(\sin \color{red}{(40 + 50)} = \sin 50 \cos 40 + \sin 40 \cos 50\)

\(\sin \color{red}{90} = \sin 50 \cos 40 + \sin 40 \cos 50\)

You do know an exact value for \(\sin 90^o\), right?

Answer 7

Its 1.

Answer 8

Correct.