What is the value of cos(40)cos(20)-sin(40)sin(20) ?

The value of cos(40)cos(20)-sin(40)sin(20) is 1/2

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cos(40)cos(20)-sin(40)sin(20)

cos (4 0^{\circ}) cos (2 0^{\circ}) - sin (4 0^{\circ}) sin (2 0^{\circ})

\frac{1}{2}

Solution steps

cos (4 0^{\circ}) cos (2 0^{\circ}) - sin (4 0^{\circ}) sin (2 0^{\circ})

Rewrite using trig identities:

cos (6 0^{\circ})

= cos (6 0^{\circ})

Use the following trivial identity:

cos (6 0^{\circ}) = \frac{1}{2}

= \frac{1}{2}

cos (3 \frac{π}{4})

tan (\frac{5}{4} π)

arctan (0.92)

50 sin (7 0^{\circ})

\frac{12.1}{sin ( 2 4 ^{\circ} )}

What is the value of cos(40)cos(20)-sin(40)sin(20) ?
The value of cos(40)cos(20)-sin(40)sin(20) is 1/2