Question

Question 10 a and b how to do plz?

Answer 1

PROOF:

Explanation:

Double angle identities:
`sin2x=2sinxcosx`
`cos2x= cos^2 x – sin^2 x`

We also know that:
`sintheta=("opposite")/("hypotenuse")`
`costheta=("adjacent")/("hypotenuse")`

Based on the given triangle,
`sintheta=b/c`
`costheta=a/c`

`sin2theta=2sinthetacostheta`
`sin2theta=2*b/c*a/c`
`sin2theta=(2ab)/c^2`

`cos2theta= cos^2theta – sin^2theta`
`cos2theta= (a/c)^2 – (b/c)^2`
`cos2theta= a^2/c^2 – b^2/c^2`
`cos2theta= [a^2 – b^2]/c^2`