What is the value of cos(15)cos(45)-sin(15)sin(45) ?

The value of cos(15)cos(45)-sin(15)sin(45) is 1/2

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cos(15)cos(45)-sin(15)sin(45)

cos (1 5^{\circ}) cos (4 5^{\circ}) - sin (1 5^{\circ}) sin (4 5^{\circ})

\frac{1}{2}

Solution steps

cos (1 5^{\circ}) cos (4 5^{\circ}) - sin (1 5^{\circ}) sin (4 5^{\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 (1.8)

tan^{2} (+ 1)

csc (arctan (- \frac{5}{12}))

- 3 sin (\frac{3 π}{2})

3 cos (4 0^{\circ})

What is the value of cos(15)cos(45)-sin(15)sin(45) ?
The value of cos(15)cos(45)-sin(15)sin(45) is 1/2