What is the value of cos(155)cos(35)+sin(155)sin(35) ?

The value of cos(155)cos(35)+sin(155)sin(35) is -1/2

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cos(155)cos(35)+sin(155)sin(35)

cos (15 5^{\circ}) cos (3 5^{\circ}) + sin (15 5^{\circ}) sin (3 5^{\circ})

- \frac{1}{2}

Solution steps

cos (15 5^{\circ}) cos (3 5^{\circ}) + sin (15 5^{\circ}) sin (3 5^{\circ})

Rewrite using trig identities:

cos (12 0^{\circ})

= cos (12 0^{\circ})

Use the following trivial identity:

cos (12 0^{\circ}) = - \frac{1}{2}

= - \frac{1}{2}

cos (24 0^{\circ} - 0^{\circ})

cot (66. 5^{\circ})

cos (10 1^{\circ})

sec (8 0^{\circ})

arctan (\frac{6}{12})

What is the value of cos(155)cos(35)+sin(155)sin(35) ?
The value of cos(155)cos(35)+sin(155)sin(35) is -1/2