Question

Cos²75+cos²15=1 without using trigonometry table

Answer 1

Answer:

LHS ,

cos²75 + cos²15

= cos²( 90 - 15) + cos² 15

= sin² 15 + cos²15

= 1 = rhs

hence proved..

Step-by-step explanation:

formula used :

1. cos( 90 - ∅) = sin∅

2. sin²∅ + cos²∅ = 1

other important formula

1. sec²∅ - tan²∅ = 1

2. cosec²∅ - cot² ∅ = 1

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