# Math Help - Another trig question

1. ## Another trig question

Value of cos65°cos12°+sin65° sin12°

-The Answer must be in either sin or cos and must be followed with a degree (i.e. cos88°)

1.6

2. Originally Posted by ceroseven
Value of cos65°cos12°+sin65° sin12°

-The Answer must be in either sin or cos and must be followed with a degree (i.e. cos88°)

1.6
You want the seccend sum or difference identity, here

Table of Trigonometric Identities

3. How would this be substituted in the equation?

4. Originally Posted by ceroseven
How would this be substituted in the equation?
Let $u=65^\circ$ and let $v=12^\circ$, then your problem reduces to

$\cos65^\circ\cos12^\circ+\sin65^\circ\sin12^\circ= \cos(65^\circ-12^\circ)=\cos53^\circ$