library(sf)

lat_lon <- data.frame(
  lat = c(86, 87, 88),
  lon = c(43, 44, 44.5)
)

lat_lon
#>   lat  lon
#> 1  86 43.0
#> 2  87 44.0
#> 3  88 44.5

# Turn this into a geometry
# EPSG 4326 is a standard coordinate reference system for lat-lon
latlon_sf <- st_as_sf(lat_lon, coords = c("lon", "lat"), crs = 4326)

# Convert to sinusoidal coordinates (in m) -- EPSG 54008
latlon_sin <- st_transform(latlon_sf, st_crs(54008))
latlon_sin
#> Simple feature collection with 3 features and 0 fields
#> geometry type:  POINT
#> dimension:      XY
#> bbox:           xmin: 173463.1 ymin: 9555197 xmax: 335023.8 ymax: 9778579
#> epsg (SRID):    54008
#> proj4string:    +proj=sinu +lon_0=0 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs
#>                   geometry
#> 1 POINT (335023.8 9555197)
#> 2 POINT (257204.5 9666887)
#> 3 POINT (173463.1 9778579)
# Note that the values are now weird and huge. That's because they are
# in `m` from a reference point (lat = 0, lon = 0)

# calculate the distance between all points
st_distance(latlon_sin)
#> Units: [m]
#>          [,1]     [,2]     [,3]
#> [1,]      0.0 136126.5 275683.1
#> [2,] 136126.5      0.0 139598.3
#> [3,] 275683.1 139598.3      0.0