Question

How can two angles be 90° in a right angle triangle as in trigonometry
Sintheta² + Costheta²=1
To prove this identity we take theta =90°
then how is it possible to call a triangle with two angles of 90° as triangle, pls help.

Answer 1

Answer:

Step-by-step explanation:

cosθsinθ - sinθcos(90°-θ)cosθ/sec(90°-θ) - cosθsin(90°-θ)sinθ/cosec(90°-θ) +cosec(90°-θ)

=cosθsinθ - sinθsinθcosθ/cosecθ - cosθcosθsinθ/secθ - secθ

=cosθsinθ - sin³θcosθ- cos³θsinθ- secθ

=cosθsinθ(1-sin²θ - cos²θ) - secθ

=cosθsinθ(1-1) - secθ

=0 - secθ

=1/cosθ = RHS