Question

value of cos 67.5 degree​

Answer 1

Answer:

Ans:

√

2

−

√

2

2

Explanation:

Call cos (67.5) = cos t. Apply the trig identity:

cos

2

t

=

2

cos

2

t

−

1

.

cos

(

135

)

=

cos

2

t

=

−

√

2

2

=

2

cos

2

t

−

1

2

cos

2

t

=

1

−

√

2

2

=

2

−

√

2

2

cos

2

t

=

2

−

√

2

4

cos

t

=

±

√

2

−

√

2

2

.

Because the arc (67.5) is in Quadrant I, its cos is positive. Therefor,

cos

(

67.5

)

=

cos

t

=

2

−

√

2

2

Check by calculator.

sin (67.5) = 0.38

sqrt(2 - sqrt2)/2 = 0.79/2 = 0.38. OK

Answer 2

Answer:

Rupees 5

paisa 70

70–5=65 is the answer