Question

(cos 420 - sin 390)(cos 420° + sin 390)(sin2 240 + sin2 390 + sin2 60)

Answer 1

Step-by-step explanation:

See Attachment Given Above⬆⬆

Answer 2

Answer:

0

Step-by-step explanation:

(cos420 - sin390)×(cos420 + sin390)×(sin²240 + sin²390 + sin²60)

[ (a-b)(a+b) = a²-b²]

=> (cos²420 - sin²390)(sin²240 + sin²390 + sin²60)

we know:- cos(360±∅) = cos∅ , sin(360±∅) = sin∅ and sin(180+ ∅) = -sin∅

so,

=> {cos²(360+60) - sin²(360+30)}{sin²(180+60) + sin²(360+30) + sin²60}

=> {cos²60 - sin²30}{(-sin60)² + sin²30 + sin²60}

=> {(1/2)² - (1/2)²}{(√3/2)² + (1/2)² + (√3/2)²}

=> 0

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