How do you find the exact value of the expression by using appropriate identities $sin(79)cos(49)-cos(79)sin(49)$ ?

Question

6504 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-12-08T03:45:13

Apply the angle addition formula to find that
$sin(79^@)cos(49^@)-cos(79^@)sin(49^@)= 1/2$

Using the identity
$sin(alpha - beta) = sin(alpha)cos(beta)-cos(alpha)sin(beta)$

$sin(79^@)cos(49^@)-cos(79^@)sin(49^@) = sin(79^@-49^@)$

$= sin(30^@)$

$= 1/2$

How do you find the exact value of the expression by using appropriate identities sin(79)cos(49)-cos(79)sin(49)sin(79)cos(49)-cos(79)sin(49)?